Make services migration more reliable

Fix for #2045 . I did not use SQL because its hard to convert SQL fields into json with interpolation and without errors. SO I just improved current migration with next:

* skip validation to prevent exception because of new `template` field in validation
* check column for existance before adding them.
  It should allow people who already failed this migration to re-run ti
* select objects with 500 batch size for better memory usage

Tested on migration from 7.0 to 7.9.0.pre

See merge request !1581

Allow non authenticated access to avatars

For #2047

cc @douwe

See merge request !1583

Ensure that people don't view the changelog on the stable branch because we don't update that one.

See merge request !1568

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