Fix importers with OCC

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/1180

Using validates_uniqueness_of does not guarantee the absence of duplicate record insertions. When users click button "import all" it will create duplicating group in database and data integrity will be broken.

http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#method-i-validates_uniqueness_of

I use optimistic concurrency control for handling this situation.

See merge request !1647

Reject access to group/project avatar if the user doesn't have access.

Closes #2050.

I'll add tests for EE logos once this is merged here and merged into EE.

See merge request !1671

Fix highlight of selected lines

* show color for highlighted line
* fix overflow by header

See merge request !1672

Properly move over `issues_tracker_id` from old custom issue tracker URLs.

Addresses https://gitlab.com/gitlab-org/gitlab-ce/issues/1124.

cc @marin Regression in 7.8.0.

See merge request !1670

Upgrade Docker build to GitLab v7.8.3

Upgrading from GitLab v7.8.1. Pretty simple change, tested with a quick Docker build.

See merge request !380

Use Gitlab::Git helper methods and constants as much as possible.

As discussed in https://dev.gitlab.org/gitlab/gitlabhq/commit/1cc41ce1adce23d3eb4a9c4ed0ab17e11ea1f1e3#note_38702.

See merge request !1668

Mention EmailsOnPush changes in changelog.

See merge request !1667

Added link generation for LinkedIn on user's Profile page

This is a very very minor change. Added a generated link to the LinkedIn portion of the user's profile.

See merge request !377

Added a link_to for the LinkedIn portion of the user's profile. It felt odd to me, having this section not being an active link like the rest of the entries on the page.

Fixing import redirect loop

While importing, don't redirect import actions to the project page, even if the repository exists

Fixes #1191

See merge request !379

Fix commit calendar to use all user emails

This MR improves upon Hannes Rosenögger's changes:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/364

See merge request !378

This MR extends the commit calendar so it searches for commits made with every email address the user has associated with his account.

This fixes one of the problems mentioned in gitlab-org/gitlab-ce#1162 and makes the behavior of the commit calendar as described in the profile.
"All email addresses will be used to identify your commits."

Blocking user does not remove him/her from project/groups but show blocked label

For #248

See merge request !1664

Add criteria for requesting CVE

For #1887. Based on https://dev.gitlab.org/gitlab/gitlabhq/issues/1945#note_34587

cc @sytse

See merge request !1662

Font size 14px

Increase base font size from 13 to 14px. We already have it in most of ui elements so no need to duplicate `font-size: 14px` everywhere - just change base variable

See merge request !1663

Apply more styles from Flatly theme

Also add bottom margin for footer links on login page

See merge request !1661