adds doubletap support
fixes tap event generation during double tap

Ensures that a tap event is sent for a control if another control is
tapped before the doubleTapInterval is reached.
reduce double tap internal to 300ms
Merge pull request #834 from enyojs/ENYO-99-ryanjduffy

Fixes ENYO-99

Reviewed-By: Cole Davis (cole.davis@lge.com)