removed socket AURA category, and logic and handling for aura contact events
remaining aura variables, masks, etc. removed
TWLMainScene includes TWLBallChangerSocket in it asset loader and puts one in the scene.
TWLSocket add a hidden "halo" node to the head.
TWLBallChangerSocket class created: this socket tells balls with single letters to switch to next letter in alphabet.
TWLBallChangerSocket is using this halo for not to show its zone of influence.
Fixed arg to waitForCompletion in sockets (was nil when should be NO).