Add "RepositoryStatusMessage" and detailed information about initilization

Summary:
`RepositoryStatusMessage` is basically a key/value table associated with a repository that I'm using to let the daemons store the most recent event of a given type, so we can easily show it on the status dashboard. I think this will be a lot easier for users to figure out than digging through logfiles.

I'm also going to write the "this needs a pull" status here eventually, for reducing the time lapse between pushes and discovery.

  - Add storage for these messages.
  - Have the pull engine populate the INIT phase. I'll do the FETCH phase next.
  - Update the status readout to show all the various states.

Test Plan: See screenshots.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7461