Allow searching in repositories
Summary: We may later integrate it in the global search but I want to leave it here too for the case that you want to search just some repository or some part of it.
Test Plan: Browsed repo in SVN and Git, searched in Git.
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, Korvin, chad
Differential Revision: https://secure.phabricator.com/D5738