Carry the "silent" transaction flag through inverse edge edits

Summary:
See PHI751. Ref T13164. We added a "silent" flag for Editors somewhat recently (currently reachable only for bulk edits with `bin/bulk ...` command).

However, this flag doesn't carry through to the sub-editor when we make inverse edge edits. These are edits like "X is a parent of Y", which cause an implicit "Y is a child of X" edit to occur.

Pass the flag through.

Test Plan:
  - Rigged the relationships controller to make silent edits.
  - Changed the parents of a revision from the web UI. Saw no mail or feed stories.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13164

Differential Revision: https://secure.phabricator.com/D19543

src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php

@@ -3599,6 +3599,7 @@ abstract class PhabricatorApplicationTransactionEditor
         ->setContinueOnMissingFields(true)
         ->setParentMessageID($this->getParentMessageID())
         ->setIsInverseEdgeEditor(true)
+        ->setIsSilent($this->getIsSilent())
         ->setActor($this->requireActor())
         ->setActingAsPHID($this->getActingAsPHID())
         ->setContentSource($this->getContentSource());