Index projects in the main search index

Summary:
Part one of a large and complicated plot:

  - The last filter for Maniphest "pro" queries is "Group By".
  - This is currently executed in a convoluted and ridiculous way, loading massive amounts of data.
  - The primary reason it works like it does is that we don't have a project name index available in Maniphest, so we can't sort in the DB.
  - So, I want to provide a name index to Maniphest and push this work to the DB.

To do that, my plan is:

  - Index projects in Search.
  - Add a "did update index" event.
  - Have Maniphest listen for it.
  - When projects are updated, update their indexes in Maniphest.
  - Rewrite the giant mess of "group by: project" to be somewhat reasonable.
  - This may also extend to some future "group by: assignee".

This is the first small step down this path, which just indexes projects in search.

Test Plan: Ran `bin/search index --type project`, then searched for projects.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D6955