Fixes grammatical consistency and small changes

This commit adds consistency to small things like periods, commas,
and gives additional information to buttons and headers, etc.

Fixes #2002, #2005, #2003.

See merge request !1570

Added information to tooltips

Tooltips now have meaning by mentioning their function ("Filter by..."). Fixes #1992

See merge request !1571

Fix import status page project links for new Rails.

Fixes #2059.

See merge request !1593

Add z index for diff header so sticky header stays on top on diff comments.

See merge request !1603

Allow mass-unassigning of issues

Fix GitLab && Gitorious importers. Hide already imported projects

Fixes #2060

See merge request !1594

Small fixes

Fixes #2062 and #2061

See merge request !1601

Fixes #867

[ci skip]

Make test element selection more specific to fix constantly failing test.

Fixes #2051.

The problem was that there were two `.note-text` elements matching `.files [id^=diff]:nth-child(2) .note-text`, one for the new comment, and one for the (currently hidden) new comment form. The latter one was selected but currently invisible, triggering the following error in poltergeist:

> The element you are trying to interact with is either not part of the DOM, or is not currently visible on the page (perhaps display: none is set). It's possible the element has been replaced by another element and you meant to interact with the new element. If so you need to do a new 'find' in order to get a reference to the new element.

This caused the test to fail.

See merge request !1592

Prevent another migration from failing due to indirect use of model columns not yet created

See https://github.com/gitlabhq/gitlabhq/issues/8817#issuecomment-76007077

cc @marin

See merge request !1597

Fix git syntax issue for git version older then 1.7.10

For #2067

See merge request !1599

Generalizes image upload in drag and drop in markdown to all files

From https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/265 by Hannes Rosenögger.

- [x] Rebase on master when !1553 is merged in

See merge request !1530

Gracefully shutdown services in Docker container

Conflicts:
	app/views/import/gitorious/status.html.haml
	db/schema.rb

Bump gemnasium service gem

# Conflicts:
#	app/controllers/files_controller.rb

UI: refactor header css

See merge request !1591

Improve admin projects and users pages for mobile devices

See merge request !1590