[Persistence] Show user, modification time

Show user name and modification time in dialog when revision-checking
detects modifications. WTD-1033.

platform/persistence/queue/src/PersistenceFailureConstants.js

@@ -2,5 +2,7 @@
 
 define({
     REVISION_ERROR_KEY: "revision",
-    OVERWRITE_KEY: "overwrite"
+    OVERWRITE_KEY: "overwrite",
+    TIMESTAMP_FORMAT: "YYYY-MM-DD HH:mm:ss\\Z",
+    UNKNOWN_USER: "unknown user"
 });