Removed dead code.
Adjust zIndex positions of all cards in the group when group is built.
- Cleans up card group listener tree.
- Returns card groups to their tableu.
Adds caching to Card.getAbsolutePosition() in order to prevent repaints.
Fixes issue #7.
Calculates drop targets on card group dragmove.
- Makes cards in a group publicly accessible.
- Optimizes for() loops.
Makes possible for card groups to change tableux. Doesn't implement any game logic yet.