[Layout] Add notion of representers

Add representers as a category of extension; these are extra
steps to perform when representing a domain object. This
will be used to support automatic mutation/persistence of
domain objects from a watch, while avoiding bloat within
the mct-representation directive itself. This, in turn,
simplifies the persistence strategy to be employed by
Layout views when editing concludes. WTD-535.

platform/representation/src/gestures/GestureRepresenter.js

@@ -0,0 +1,37 @@
+/*global define*/
+
+define(
+    [],
+    function () {
+        "use strict";
+
+        function GestureRepresenter(gestureService, scope, element) {
+            var gestureHandle;
+
+            function destroy() {
+                if (gestureHandle) {
+                    gestureHandle.destroy();
+                }
+            }
+
+            function represent(representation, domainObject) {
+                // Clear out any existing gestures
+                destroy();
+
+                // Attach gestures - by way of the service.
+                gestureHandle = gestureService.attachGestures(
+                    element,
+                    domainObject,
+                    (representation || {}).gestures || []
+                );
+            }
+
+            return {
+                represent: represent,
+                destroy: destroy
+            };
+        }
+
+        return GestureRepresenter;
+    }
+);