Add a Pointer Click Listener

Right now we have Pointer Down and Pointer Up, but no Pointer Click. Creating an comprehensive onClick event with the current listeners takes some extra steps. Ex:

• When the user touches the button ( Pointer Down ) set an isDown to true.

• If they release the button ( Pointer Up ) over the same hit area and isDown == true , it's a click.

• If they move their finger off the button before releasing, set isDown to false (not exactly how the JS onClick works, but good enough)

It'd be nice to have a built-in click listener that doesn't require all this extra setup.