Phabricator: Extend CONDUIT API to support xaction transactions

Example of null transactions and their expected value:

* D9:transaction 44 - "abandon"
* D22:transaction 112 - "commit"
* D22:transaction 96 - "accept"
* D1123:transaction 22872 - "rethink"

Reviewers: sergey

https://developer.blender.org/D11568

src/applications/transactions/conduit/TransactionSearchConduitAPIMethod.php

@@ -295,7 +295,13 @@ EOREMARKUP
               'new' => $xaction->getNewValue(),
             );
             break;
-
+          case DifferentialTransaction::TYPE_ACTION:
+            $type = DifferentialTransaction::TYPE_ACTION;
+            $fields = array(
+              'old' => $xaction->getOldValue(),
+              'new' => $xaction->getNewValue(),
+            );
+            break;
         }
       }