Use an inline dialog element for inline comments in Differential

Summary:
The current approach of using a modal overlay dialog to create/edit inline
comments is pretty silly. Use an inline textarea instead.

This element isn't perfect and we have some mild modalness issues, but I think
it's better than the silly thing we've got going on right now. We can keep
poking it as people break it.

Test Plan:
  - Created comments; submitted and undid them in empty and nonempty states.
Used undo for nonempty states + cancel.
  - Edited comments; saved and canceled them. Used undo for changed state.
  - Replied to comments; yada yada as above.
  - Deleted comments.
  - Did various modal trickery where I clicked "Reply" on something else with a
dialog already up, this very mildly glitches but I think it's not a big issue.

Reviewers: vrana, btrahan, Makinde, nh

Reviewed By: vrana

CC: aran, epriestley

Maniphest Tasks: T431

Differential Revision: https://secure.phabricator.com/D1716

src/applications/differential/view/changesetlistview/DifferentialChangesetListView.php

@@ -212,13 +212,17 @@ class DifferentialChangesetListView extends AphrontView {
       Javelin::initBehavior('differential-edit-inline-comments', array(
         'uri' => '/differential/comment/inline/edit/'.$revision->getID().'/',
         'undo_templates' => $undo_templates,
+        'stage' => 'differential-review-stage',
       ));
     }
 
-    return
-      '<div class="differential-review-stage" id="differential-review-stage">'.
-        implode("\n", $output).
-      '</div>';
+    return phutil_render_tag(
+      'div',
+      array(
+        'class' => 'differential-review-stage',
+        'id'    => 'differential-review-stage',
+      ),
+      implode("\n", $output));
   }
 
   /**