Basic gameplay is functional.  You can tap only on the ball to cause
it to move upwards in the scene.

We're also calculating where inside the ball you touched and using that
when calculating the impulse vector to apply to the ball.

Also moving away from the .sks file and towards pure code implemenation
of the game.

Fixes indentation (moved towards 2-char indent) of viewController
and moves Scene initilization code into separate function for easy
swapping between initialization via code or .sks file.