[Containment] Fire compose instead of link

Fire compose instead of link on drop, since this will
match usage for move/copy/link in the future. WTD-962.

platform/representation/src/gestures/DropGesture.js

@@ -55,7 +55,7 @@ define(
                 if (selectedObject) {
                     // TODO: Vary this based on modifier keys
                     action = actionCapability.getActions({
-                        key: 'link',
+                        key: 'compose',
                         selectedObject: selectedObject
                     })[0];