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

Conflicts:
	doc/installation.md

Fix merge mess in installation.md

2. SSH Keys Help page

Styled Wiki edit page

* .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

The current overview is a mess.
This pull commit will make it look more clean.

All permissions are alliged between the columns and the master rights
have been enchanced with all its rights.