Selecting a branch is dangerous now that we have rc in a branch.
Change it earlier as well.
added office analogy to help understanding of gitlab architecture
replaced hotlink
remove unnecessarry image
Update time zone rake task for production. Resolves #8387
add details on protected branches

Add some details from https://about.gitlab.com/2014/11/26/keeping-your-code-protected/:

Who can:
* Force push to non-protected branches
* Force push to protected branches
* Remove protected branches
Add Dockerfile to build an Omnibus GitLab image
teamcity basic support