Rewrite and improve git backend logic. Fix project movind. Raise exception to prevent unexpected issues

- Add project name to event title
- Push: Entry links to single commit or commits overview depending on number of pushed commits
- Push: Display first 15 commits with commit message and author and link to single commit
- Issues: Display issue description

Merge branch 'master' into non-interactive-aws-install

Conflicts:
	doc/installation.md

Fix merge mess in installation.md

2. SSH Keys Help page

Didn't bother with files in db/, config/, or features/

Changed "authored or assigned to you" to read "authored by or assigned to you" which reads better.

* .page_title  class added. Used for better page headers
* improved help page
* added back links for help pages
* show app version & revision on help page

Backend changes:
* Gitab::Version && Gitlab::Revision constants

* dashboard should be in dashboard controller not project index
* projects index removed