Add tracker integration doc and help page on service

Added documentation on how to enable tracker integration. Fix the active link on the admin page. Added help under the JIRA service page.

See merge request !1508

Add headings to signin/signup blocks on signin page.

See #1986

![Screen Shot 2015-02-13 at 15.17.34](https://dev.gitlab.org/uploads/gitlab/gitlabhq/4feb067a23/Screen_Shot_2015-02-13_at_15.17.34.png)

When signup is disabled, the heading for sign in only reads "Sign in", because there is no longer a choice of Existing/New user.

I've moved the OAuth signin options to just below the signin box because it looked odd as a separate box without a heading.

cc @sytse

See merge request !1516

 Add "New Project" button to dashboard projects page.

See merge request !1518

Link head panel titles to relevant root page.

I found myself trying to click "GitLab" in the head panel when on the group milestones page.

See merge request !1515

Rspec upgrade

Clean username acquired from OAuth/LDAP.

Fixes #1967.
Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/813

See merge request !1500

Show assignees in the merge-requests index

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Use gitattribute merge=union to reduce CHANGELOG merge conflicts.

See gitlab/organization#137.

Tested and found working!

@sytse How would you like to address this in [the article](https://about.gitlab.com/2015/02/10/gitlab-reduced-merge-conflicts-by-90-percent-with-changelog-placeholders/)? Simply replace "Thanks ayufan, we'll try this instead." by "Thanks ayufan, we've implemented this instead."?

See merge request !1505

Fixes #1967.

Issues trackers template

If admin defines service template, service in project will be prefilled with the template data.

See merge request !1503

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

requests/api/project_spec.rb speed up

note about latest details being on master branch

Adds new label color suggestions

This adds a bunch of label color suggestions

![labels2](https://gitlab.com/uploads/gitlab-org/gitlab-ce/ac1a207575/labels2.png)
![labels1](https://gitlab.com/uploads/benny/gitlab-ce/d47fbecc16/labels1.png)

See merge request !289

Edit group members via API

Fixes #1840.  Implement a new API endpoint to update the access level of an existing group member.  Includes new tests and updated API docs.

cc @sytse @douwe

See merge request !1504