Backport custom dashboard

This is a backport of !778 without the `Gitlab::Themes` refactor for the 7.12 branch.

See merge request !828

Bump rails to 4.1.11, jquery-rails to 3.1.3 for stable

See merge request !832

Bump rails to 4.1.11, jquery-rails to 3.1.3

rails 4.1.11 notes - http://weblog.rubyonrails.org/2015/6/16/Rails-3-2-22-4-1-11-and-4-2-2-have-been-released-and-more/

jquery-rails < 3.1.3 security advisory: https://groups.google.com/forum/#!topic/ruby-security-ann/XIZPbobuwaY

See merge request !830

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Also converts doc/README.md to Unix line endings

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This controller is now the target for `root_url`. It sub-classes
DashboardController so we can render the old default without a redirect
if the user hasn't customized their dashboard location.

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It was only used for the appearance live updating, which is now handled
by Profiles::Preferences#update

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Kerberos require to stable 7.12

!819 to 7-12-stable

cc @jacobvosmaer

See merge request !827

If kerberos is enabled require it

Since 'group: :kerberos' got [included in the Gemfile ](https://gitlab.com/gitlab-org/gitlab-ce/commit/2391a43a7073b4e723e9ca1f7ff19b30f8e51452) Kerberos no longer got [loaded when the app started](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/config/application.rb#L6)

This caused `Devise::OmniAuth::StrategyNotFound` error once Kerberos is enabled, failing to start GitLab .

With this we hopefully do not need to remove group from the Gemfile.

See merge request !819

Fixes for RC2

we need it to make GitLab works with new CI

cc @jacobvosmaer

See merge request !1864

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

Look for .gitlab-ci.yml only if checkout_sha is present

Fixes https://dev.gitlab.org/gitlab/gitlabhq/issues/2396

cc @vsizov

See merge request !818

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

Update install docs for 7.12

See merge request !1857

Even though the 7-12-stable branch does not exist yet.

Git 2.1.2 does not protect against pushes trying the '.Git/config'
attack (CVE-2014-9390). Going to 2.4.3 is perhaps a big jump but why not
use the latest? (Famous last words.)

Remove text since rss is now to prominent.

See merge request !1855

Fix link to howto_rc1.md

The relative link that was there before breaks when you copy-paste the
issue template into an actual issue.

See merge request !1856