R1:83efa6e1c5c8

make arc diff link maniphest tasks with revisions

Summary:
add "Maniphest Task:" or "Maniphest Tasks:" followed by text that has TX in it.
foreach TX the task will be attached to the revision and the revision will be
attached to the task. parsing is pretty... ummm, robust such that it will pick
up any TX substring and parse that as a Maniphest Task just fine. it errors
out if there is not an actual task for TX and otherwise churns along pretty
nicely.

Also, make sure the PhabricatorObjectHandle loads…