Unify Maniphest + Differential comment styles

Summary:
I want to add comments to commits, and they should obviously share code with the
nearly-identical comments in Maniphest and Differential. Unify code/style as
much as possible.

This program made possible by a generous grant from D1513.

Test Plan:
  - Looked at a bunch of different Differential and Maniphest comments; they
appeared to render identically to how they looked before.
  - Tested some edge cases like anchors and "show details" on description edits
in Maniphest.

Reviewers: btrahan, jungejason

Reviewed By: btrahan

CC: aran, epriestley

Maniphest Tasks: T904

Differential Revision: https://secure.phabricator.com/D1686

src/__phutil_library_map__.php

@@ -784,6 +784,7 @@ phutil_register_library_map(array(
     'PhabricatorTimelineEventData' => 'infrastructure/daemon/timeline/storage/eventdata',
     'PhabricatorTimelineIterator' => 'infrastructure/daemon/timeline/cursor/iterator',
     'PhabricatorTimer' => 'applications/countdown/storage/timer',
+    'PhabricatorTransactionView' => 'view/layout/transaction',
     'PhabricatorTransformedFile' => 'applications/files/storage/transformed',
     'PhabricatorTrivialTestCase' => 'infrastructure/testing/testcase/__tests__',
     'PhabricatorTypeaheadCommonDatasourceController' => 'applications/typeahead/controller/common',
@@ -1503,6 +1504,7 @@ phutil_register_library_map(array(
     'PhabricatorTimelineEvent' => 'PhabricatorTimelineDAO',
     'PhabricatorTimelineEventData' => 'PhabricatorTimelineDAO',
     'PhabricatorTimer' => 'PhabricatorCountdownDAO',
+    'PhabricatorTransactionView' => 'AphrontView',
     'PhabricatorTransformedFile' => 'PhabricatorFileDAO',
     'PhabricatorTrivialTestCase' => 'PhabricatorTestCase',
     'PhabricatorTypeaheadCommonDatasourceController' => 'PhabricatorTypeaheadDatasourceController',