Add _bubble_target setting to enyo.ViewController, matching override used by enyo.Application to allow events to bubble up from owned view.

Enyo-DCO-1.1-Signed-Off-By: Ben Combee (ben.combee@lge.com)
Merge pull request #355 from enyojs/bubble-to-viewcontroller

Add _bubble_target setting to enyo.ViewController, matching override use...