Wrap all rate limiting logic inside GitHub API client

## What does this MR do?

Move the actual rate limiting logic to GitHub API to clean the code inside the GitHub importer, and avoid code duplication.

## Are there points in the code the reviewer needs to double check?

No there aren't.

## Why was this MR needed?

Avoid code duplication to handle API rate limit in every call to the GitHub API.

## What are the relevant issue numbers?

There are none.

## Screenshots (if relevant)

Not relevant.

See merge request !4552

Fix failing `EmailOnPush` spec.

Closes #18447 

- This should fix CI on master

/cc @smcgivern @ayufan @stanhu @pacoguzman 

See merge request !4582

Award emoji fixes

Fixes #18357 #18325 and #18424

See merge request !4550

yes -> true
no -> false
. frequent -> .frequent-emojis

[ci skip]

Properly quote table name in Rake task for MySQL and PostgreSQL compatibility

!4318 broke the gitlab:db:drop_tables functionality for PostgreSQL.
    
Closes #15259

See merge request !4577

Add milestone expire date to the right sidebar

## What does this MR do?
Shows milestone expire date tooltip in the sidebar. It also shows the tooltip when sidebar is collapsed.

## Are there points in the code the reviewer needs to double check?
`common_utils.js.coffee` and `milestones_helper.rb` should be reviewed deeply.

## What are the relevant issue numbers?
https://gitlab.com/gitlab-org/gitlab-ce/issues/17355

## Screencast
![zngAcytBWq](/uploads/bd8514506aa5010aef9b081455ee90af/zngAcytBWq.gif)

See merge request !4448

!4318 broke the gitlab:db:drop_tables functionality for PostgreSQL.

Closes #15259

Checks for undefined when inserting autocomplete into textarea

## What does this MR do?

Correctly checks for undefined before inserting anything into the textarea when using autocomplete. This happens because the loading indicator tries to insert `@undefined` which we dont want to insert.

See merge request !4561

Fix bug with SQL syntax error during backup restoration

## What does this MR do?
It properly escapes the table name in the `DROP TABLE IF EXISTS ...` statement used during restore of a backup.

## Are there points in the code the reviewer needs to double check?
Please check compatibility with PostgreSQL

## Why was this MR needed?
Fix an issue with backups can not be restored if MySQL is used as database for GitLab.

## What are the relevant issue numbers?
#15259 

## Screenshots (if relevant)
-

See merge request !4318

Fix empty user projects snippets list

## What are the relevant issue numbers?
Closes #17952 #17816 and  #17737 

cc: @lbennett  @jschatz1 

See merge request !4532

Improve ui consistency. Part 2

* Use responsive top-area on project branches and tags pages
* Use default button size in the content list controls
* Improve button margin for btn-grouped css class

For https://gitlab.com/gitlab-org/gitlab-ce/issues/18324

See merge request !4536

Improved the UX of issue & milestone date picker

## What does this MR do?

Improves the UX of the date picker on issue form & milestone form.

## What are the relevant issue numbers?

Closes #18198 

## Screenshots (if relevant)

### Issues

![Screen_Shot_2016-06-06_at_09.28.29](/uploads/d9c192dff0d8076adc3ed6f005ea3790/Screen_Shot_2016-06-06_at_09.28.29.png)

### Project milestones

![Screen_Shot_2016-06-06_at_09.28.18](/uploads/2d03d72791c5fc6badfadb975a85af2b/Screen_Shot_2016-06-06_at_09.28.18.png)

### Group milestones

![Screen_Shot_2016-06-06_at_09.28.05](/uploads/0f28532396a16e6fd48ddea784ca28e3/Screen_Shot_2016-06-06_at_09.28.05.png)

See merge request !4485

Only load Chart.js when necessary.

Only load Chart.js where it's used, namely the Graphs section. Follow up on !4394.

cc: @jschatz1 

See merge request !4516

Fix local timeago on user dashboard

## What does this MR do?
Fixes incorrect date times on tooltips on the dashboard page

## Are there points in the code the reviewer needs to double check?
Yes,  The tooltip has to be recreated again because we needed a custom CSS classname in order to fix the date being splitted into two lines.

## Why was this MR needed?
Because the datetimes were incorrect we have to have the same format for .timeago() instances.

## What are the relevant issue numbers?
#17607

## Screenshots (if relevant)

**Before**

<img src="/uploads/f40cd58e8086d9675262e98a1fe57885/Screen_Shot_2016-05-24_at_7.23.25_PM.png" width="705">

**After**

<img src="/uploads/bd48046ef11659cc742f827b3404fbcd/Screen_Shot_2016-05-24_at_7.22.29_PM.png" width="704">


See merge request !4285

Improve input padding, fix #18237.

## What does this MR do?
Improves horizontal padding for input fields.

## What are the relevant issue numbers?
#18237

## Screenshots (if relevant)

Before:

![Screen_Shot_2016-06-06_at_12.11.07_PM](/uploads/11d24c84e1ca8d268a5acc2b4e10bb77/Screen_Shot_2016-06-06_at_12.11.07_PM.png)

After:

![Screen_Shot_2016-06-06_at_12.10.38_PM](/uploads/cbb407d8fca1e8dc1ace2af6c0774181/Screen_Shot_2016-06-06_at_12.10.38_PM.png)

cc: @jschatz1 

See merge request !4489

Use warning color merge conflicts icon in MR status widget.

Fixes #18174 

### Before
![Screen_Shot_2016-06-06_at_18.00.56](/uploads/4a74b1710478daee5ee95b7c6b6a835f/Screen_Shot_2016-06-06_at_18.00.56.png)

### After
![Screen_Shot_2016-06-06_at_17.58.04](/uploads/28faefaebef30e4256390029c87b28bb/Screen_Shot_2016-06-06_at_17.58.04.png)

See merge request !4487

Closes #18198

Edit form background color on highlighted note

## What does this MR do?

Added white background to edit form when in a highlighted note

## What are the relevant issue numbers?

Closes #18101 

## Screenshots (if relevant)

![Screen_Shot_2016-06-02_at_11.24.20](/uploads/c7c7fe710aa74d86152a109560fd0ebe/Screen_Shot_2016-06-02_at_11.24.20.png)

See merge request !4435

Toggling a task in a description with mentions doesn't creates a Todo

When user toggle a task list item in a description with a mention it
does not create an unnecessary Todo for that mention.

Closes #14116

See merge request !4568

Blur button tags when pressed to remove the focus state.

## Before 

![pemnD5exKl](/uploads/333155bf4a6c43715f3fc04d8f5aa35e/pemnD5exKl.gif)


## After

![dCPvSwsuWp](/uploads/9bcfbe59ac8de51e9d2c3edcb3d13ff3/dCPvSwsuWp.gif)

See merge request !4418

Updated labels UI

- Fixed alignment issues
- Added dropdown to mobile to make the options look nicer & to save space

![Screen_Shot_2016-05-25_at_09.42.46](/uploads/ff59abd2310725965b388a62c6c1f2af/Screen_Shot_2016-05-25_at_09.42.46.png)

Closes #14227

See merge request !4273

#17562 Fixes issues list filter only visible when user is logged in

## What does this MR do?

1. Moves the issue/MR list search form out of the `if current_user` conditional, allowing guests to view the field.

2.  Adds some margin to the search form, this is because in mobile view for guest users, the field was not supported by the RSS button and the New Issue button and would drop to meet the list.

## Are there points in the code the reviewer needs to double check?

Are there any views where the `margin-bottom: 12px` will affect the styling?

## Why was this MR needed?

Guest user UX. Nothing feels better than increasing intangible value!

## What are the relevant issue numbers?

Fixes #17562.

## Screenshots (if relevant)

![Screen_Shot_2016-05-16_at_23.48.06](/uploads/cf0f0c48287517ac3e83b204b4ee09b2/Screen_Shot_2016-05-16_at_23.48.06.png)

/cc @jschatz1 

**UPDATE:**

![Screen_Shot_2016-05-20_at_16.13.22](/uploads/eb854838a514d0d54d0f13bde1636b8a/Screen_Shot_2016-05-20_at_16.13.22.png)

See merge request !4171

Fix 2FA-based login for LDAP users

The OTP input form is shared by both LDAP and standard logins, but when
coming from an LDAP-based form, the form parameters aren't nested in a
Hash based on the `resource_name` value.

Now we check for a nested `remember_me` parameter and use that if it
exists, or fall back to the non-nested parameters if it doesn't.

Somewhat confusingly, the OTP input form _does_ nest parameters under
the `resource_name`, regardless of what type of login we're coming from,
so that allows everything else to work as normal.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/18185

See merge request !4493

Update CHANGELOG

Fixes wrong changelog entry for !4175

See merge request !4548