Gitlab.com importer: Doc && screenshots

See merge request !1520

Allow users that signed up via OAuth to set their password in order to use Git over HTTP(S)

See #1982.

![Screen Shot 2015-02-13 at 13.37.28](https://dev.gitlab.org/uploads/gitlab/gitlabhq/69fe527252/Screen_Shot_2015-02-13_at_13.37.28.png)

There's a similar tooltip for SSH: "Add an SSH key to your profile to pull or push via SSH". These are always shown on-hover, even if the persistent flash above was hidden.

cc @sytse

See merge request !1512

Prevent autogenerated OAuth username to clash with existing namespace.

If the OAuth username already exists as a group rather than a user, automatic account creation would still fail.

See merge request !1511

Log documentation

See merge request !1513

Oauth2 provider doc

See merge request !1519

Test settings for issue tracker service

This adds minimum logging and response when using "test settings" button when the service is enabled.

See merge request !1506

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>