R1:9367c41a2840

Tasks can be defined in the commit message (Phabricator part).

Summary:
Phabricator did not support giving the task ids in the commit message.
Currently there is no default implementation for this, but there is a
Facebook specific implementation. At some point default implementation
for Maniphest tasks to revisions will be added.

Test Plan:
Tested with the Facebook specific implementation that task ids are
recognized in the commit message and tasks are automatically attached
to revisions.

The task…