Archiving old projects for feature request

Created by: Popl7

as a solution for Feature Request: http://feedback.gitlab.com/forums/176466-general/suggestions/3841424-archiving-old-projects

I have added the archiving of projects.

The archived projects aren't shown on the dashboard. They can be found on the projects page and are marked as 'archived'.

Only limit commits and merges for archived projects by changed in the ability.

I have added features for archive projects. Tests for the rights to the archived project must still be made.