Improve error messages when file editing fails

Give more specific errors in API responses and web UI flash messages when a file update fails.  See #1479.

Instead of returning false from `Gitlab::Satellite::Files::EditFileAction#commit!` when a `Grit::Git::CommandFailed` error is raised, now `#commit!` raises a different error depending on whether the failure happened during checkout, commit, or push.

@dzaporozhets Please let me know if you want to change the HTTP status codes or the error messages in `Files::UpdateService`

cc @sytse

See merge request !1569

Fix ZenMode on commit show and milestone edit pages.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/1110

See merge request !1557

Git Clone btn more apparent

Added a faint background to the button to show that it is in an
active state for the user. White background is often hard to tell
if something is being pushed, so adding a "shadow" makes it a bit
easier to tell.

Fixes #1998

See merge request !1577

Added a faint background to the button to show that it is in an
active state for the user. White background is often hard to tell
if something is being pushed, so adding a "shadow" makes it a bit
easier to tell. Fixes #1998

Update 7.7-to-7.8.md

Bump GitLab for Docker to version 7.8.0

See merge request !347

Small spelling correction

There's a small spelling error on the project settings page. 'an project' is not correct English.

See merge request !348

Give more specific errors in API responses and web UI flash messages
when a file update fails.

Upgrade to Rails 4.1.9

Upgrade the Rails gem to 4.1.9.  Rails behavior changed in version 4.1.2, requiring that we avoid using slashes in arguments to path helpers.  This MR changes routing to use nested resources for that reason.

TODO:

* [x] Make Spinach tests green
* [x] Make it mergeable

cc @sytse @dzaporozhets

See merge request !1494

Conflicts:
	app/views/dashboard/projects.html.haml

Update gitlab-shell to 2.5.3 in 7-8 update guide, fixes #8838

UI improvements

* filter tabs for dashboard projects page
* handle all sidebars on mobile with Aside javascript class
* remove semantic ui dependency
* fix broken sidebar for dsahboard

See merge request !1567

Move Rails 4.1.9 changes to version 7.9.

Conflicts:
	app/views/projects/commits/_commit.html.haml
	app/views/projects/issues/_issue.html.haml
	app/views/projects/issues/_issue_context.html.haml
	app/views/projects/merge_requests/_merge_request.html.haml
	app/views/projects/merge_requests/show/_context.html.haml

Change check to only swap static middleware when it's enabled.

Fixes problem with #1553.

cc @marin

See merge request !1565

Fix commit comments on first line of diff not rendering in Merge Request Discussion view.

Example can be seen near the bottom on this MR: !1533.

Before:

![Screen Shot 2015-02-20 at 10.24.34](https://dev.gitlab.org/uploads/gitlab/gitlabhq/35600b98b5/Screen_Shot_2015-02-20_at_10.24.34.png)

After: the [note](https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/1533/diffs#note_36449) is actually rendered.

See merge request !1552

Redirect from /tree/master on empty repo instead of showing 404.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/1114

See merge request !1559

Merge branch 'go-get-workaround-nginx' of https://github.com/mattes/gitlabhq into mattes-go-get-workaround-nginx

Conflicts:
	lib/support/nginx/gitlab
	lib/support/nginx/gitlab-ssl

Base new MR description on commit description if there's only one.

Closes #2029, again.

See merge request !1561

Fix note attachments XSS and access control

Replaces the reverted #1528, as proposed in https://gitlab.com/gitlab-org/omnibus-gitlab/issues/434, as discussed with @dzaporozhets and as summarized in #2032.

@marin Could you take a look at the nginx config and apply it to Omnibus once this gets merged?

See merge request !1553