Fixes ENYO-99

### Issue:
While not a preferred UX pattern, need to add double tap support to the framework for specific use cases.

* Should be enable-able at the framework and control level.
* Needs to be implemented purely at JavaScript level (no WebKit support).

### Fix:
Before sending a tap event, check for doubleTapEnabled. If yes, set a Timeout. If another tap comes before timeout expires, send a double tap event. If timeout fires, send a tap event

Enyo-DCO-1.1-Signed-off-by: Ryan Duffy <ryan.duffy@lge.com>
What was the reason for settling on 400ms here? If you guys tested it and it was _best_ this way, then fine, but I think I've seen where WebKit and Firefox both use 300...