Adds -swipe, -tap and -pinch helper methods to UIView to allow for the triggering of the appropriate UIGestureRecognizers (if they have been added to the view).

We've not implemented the full set of standard UIGestureRecognizers, but this should be fairly straightforward given the code we have added.

Requested by @sweetleon.
Backfill some tests for a straightforward category method on UIView