Merge CI into CE

First step of #2164.

- [x] Merge latest CE master
- [x] Make application start
- [x] Re-use gitlab sessions (remove CI oauth part)
- [x] Get rid of gitlab_ci.yml config
- [x] Make tests start
- [x] Make most CI features works
- [x] Make tests green
- [x] Write migration documentation
- [x] Add CI builds to CE backup

See merge request !1204

Fix broken sort in merge request API

This MR fixes a bug in the API in querying for merge requests with a `sort_by` field would never change the ordering of the results.

Closes #2266

See merge request !1305

Expand Reply by email documentation

TODO:

- [x] Verify this works on dev server
- [ ] Figure out SSL somehow: http://www.postfix.org/TLS_README.html (Moved to #2453)

See merge request !1193

Closes #2266

Sorted autocomplete users list by name

bump fogbugz gem

- Change Notify to Ci::Notify
- Downgrade sidekiq to fix CE errors: otherwise we need to check deliverables

This reverts commit 345ff6cb.

This requires sidekiq >= 3.4 and fixed all other CE tests

Cleanup some html/css for upload feature

* fix colors to match UI style
* cleanup templates from meaningless code
* improve placeholders
* remove code duplication in template
* improve error handling: remove file automatically

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

For #2520

See merge request !1297

# Conflicts:
#	Gemfile.lock

Add a help text to the Slack Service

When setting up the service I was not sure which webhook I should use, by adding
this Help text I hope we can help people in the future with setting up this hook

See merge request !1302

Dynamically adjust placedholder for uploads and fix Dropzone event handlers

Override error handler to prevent error messages from being inserted underneath image preview

Fix tests

Use regexp instead of startsWith for better browser compatibility

Remove duplicate code in _replace.html.haml and use one template

Remove files upon error and retain alert messages until user adds a new file

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Use fixed version of fogbugz gem