Provide and populate an object name index for Maniphest

Summary: See discussion in D6955. This provides a table we can JOIN against to (effectively) "ORDER BY project name", populates it intially, and keeps it up to date as projects are edited.

Test Plan:
  - Ran storage upgrade, verified projects populated into the table.
  - Edited a project, verified its entry updated.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D6957