Fix OAuth2 issue importing a new project from GitHub and GitLab

It appears that the GitLab OAuth2 client options were converted to strings instead of symbols when merged with the default options (i.e. `{}.merge(github_options)`). As a result, the OAuth2 defaults were being used. For example, the OAuth2 client options would have a key with `authorize_url` and `:authorize_url`, but the former was never used. As a result, the OAuth2 client would always use the wrong URL to talk to GitHub.

Note that this bug should also have affected GitLab, but not Bitbucket: The OAuth client is careful to convert all keys to symbols.

Closes #1268

See merge request !425

Return a `SafeBuffer` instead of a `String` from the `#gfm_with_options`
method so that Rails doesn't escape our markup.

Also add `<span>` to the sanitization whitelist to avoid breaking syntax
highlighting in code blocks.

Closes #1268

Disable reference generation in preformatted/code blocks

### Summary

If a user adds text in code or preformatted text via Markdown or HTML that contains `#XXX`, the system adds a note that issue `XXX` was mentioned. This is particularly annoying because we often list gdb backtrace dumps into our issues, and many issues get mentioned as a result. For example:

```
(gdb) bt
#0  0x00000000004004c4 in second () at main.cc:6
#1  0x00000000004004d2 in first () at main.cc:11
#2  0x00000000004004dd in main () at main.cc:17
(gdb)
```

### Steps to reproduce

1. In an issue, write the above text using Markdown or HTML tags (e.g. `<code>`, `<pre>`).
2. Observe that [issue 1](https://gitlab.com/gitlab-org/gitlab-ce/issues/1) and [issue 2](https://gitlab.com/gitlab-org/gitlab-ce/issues/2) have a note that says they were mentioned.

### Expected behavior

Everything enclosed in the code blocks should be ignored as references.

### Observed behavior

Issues get referenced unnecessarily.

### Fix

I've made `reference_extractor.rb` strip out HTML and Markdown blocks before processing. I considered running the raw text through the entire Markdown processor, but this seems overkill and perhaps could lead to some unintended side effects.

See merge request !365

Fix dots in Wiki slug causing errors

### What does this MR do?

When a user enters in dots into the Wiki slug, an error occurs:

```
NoMethodError (undefined method `escaped_url_path' for nil:NilClass):
  app/models/wiki_page.rb:172:in `set_attributes'
  app/models/wiki_page.rb:191:in `save'
  app/models/wiki_page.rb:155:in `update'
  app/controllers/projects/wikis_controller.rb:49:in `update'
```

This MR fixes this problem.

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

See the problem below.

### Why was this MR needed?

The issue is that the `save` method gets called differently:

```ruby
def create(attr = {})
....
    save :create_page, title, content, format, message
```

or

```ruby
def update(new_content = "", format = :markdown, message = nil)
...
    save :update_page, @page, content, format, message
```

In the create case, title is the slug entered in by the user (e.g. `path/how-to-write-wiki-pages`).

In the update case, originally `@page.page` included the format extension (e.g.`path/how-to-write-wiki-pages.Markdown`). The method `page_title_and_dir` was trying to handle both cases and not doing the right thing. For example, calling `page_title_and_dir('test-1.2.3')` would result in:

```
path_title = test-1.2
path_dir = 3
```

### What are the relevant issue numbers / [Feature requests](http://feedback.gitlab.com/)?

Issues #1263, #431

This replaces !156

See merge request !419

Updated upgrader.md to highlight nodejs as required package [ci skip]

Updated upgrader.md to highlight nodejs pacakage so this is kept consistent with the other packages listed as required/changed.

This is purely a documentation change.

See merge request !424

Fix "Import projects from" button to show the correct instructions

Closes #1267

See merge request !422

Remove the "unreleased" word from v7.9.0 changelog

Remove old GitLab auth image

Remove `gitlab_64.png_old` because it seems to to be an artifact.

Related to !419

See merge request !421

Closes #1267

Improve profile

### OLD

![old-oauth](https://gitlab.com/gitlab-org/gitlab-ce/uploads/86f4b19d4e4cc9cf2705400428541a82/old-oauth.png)

### NEW

![profile](https://gitlab.com/gitlab-org/gitlab-ce/uploads/c480372e66af579ce355d5c215669296/profile.png)

See merge request !418

Closes #1263, #431

Change permissions on backup files - #2

Use more restrictive permissions for backup tar files and for the db, uploads, and repositories directories inside the tar files.  See #1894.  Now the backup task recursively `chmod`s the `db/`, `uploads/`, and `repositories/` folders with 0700 permissions, and the tar file is created as 0600.

This is a followup to !1703, which was reverted because it broke Rspec tests.  The test failures were due to the rake task changing directories and not changing back, which I fixed with this commit.

cc @sytse

See merge request !1716

Add sidetiq dependency

Add the sidetiq gem to the Gemfile to match EE.  See #2159.

cc @sytse

See merge request !1734

Merge branch 'topic/push_tag_events_for_ci' of https://github.com/ayufan/gitlabhq into ayufan-topic/push_tag_events_for_ci

Performance improvements

* Cache project branches and tags into variables
* Cache lookup results into hash to prevent repeating same requests to git repo
* Cache head commit and head tree

See merge request !417

Fix link in patch update guide

Use an absolute URL to gitlab.com's master branch instead of a relative URL on the local instance.  Also change which words are include in the anchor element, since the Markdown parser doesn't seem to like backticks inside the link text.

### Before

![update_link_before](https://dev.gitlab.org/Okada/gitlabhq/uploads/f6a8b2aa06ca210d5ea8a8b28a78c30c/update_link_before.png)

### After

![update_link_after](https://dev.gitlab.org/Okada/gitlabhq/uploads/6df92b3f5d8ffd6906bdc62cf19acb11/update_link_after.png)

cc @sytse

See merge request !1735

Hide UI elements when print md files or wiki pages

Fixes #1023

See merge request !416

Add the sidetiq gem to the Gemfile to match EE.

Merge updated CHANGELOG entries

Improve header with avatar for group and user pages

Nice looking and aligned headers for user and group pages

See merge request !412