Observe issue, merge request, note creation - create event
register push event

ProtectedBranches model, Master permission for repo\n Allow push to protected branch for masters only

Project - restyled show page, removed info page
Repository - restyled show page, added download option
Tags - added download options

Project activities perfomance increased. Cache for project activitites disabled. Repository conception changed

We don't execute web hooks when:
 * You create a new branch. Make sure you first create the branch, and then push any commits. This is the way Github works, so its expected behavior.
 * When tags are pushed.

This commit includes:

 * Projects can have zero or more WebHooks.
 * The PostReceive job will ask a project to execute any web hooks defined for that project.
 * WebHook has a URL, we post Github-compatible JSON to that URL.
 * Failure to execute a WebHook will be silently ignored.