Fixes #1830

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

Conflicts:
	doc/installation.md

Fix merge mess in installation.md

Continues #1222

Closes #1222

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

buttons on forms are disabled on submit (re-enabled after the request is complete)

* .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