Our Layer subclasses are missing touch handling

[andymatuschak]

Layer's view is a special UIView subclass which has some additional features—most notably, key parts of the touchBeganHandler implementation. As a consequence, touch handling doesn't work on e.g. text layers, video layers, etc.

The Layer subclasses all use their own view subclasses. There's no multiple inheritance, so we'll need to use composition instead (i.e. make those custom views be a subview of Layer's special view), not be the layer's view.

/cc @jbrennan

[jbrennan]

Deuce.