Merge pull request #11 from jperedadnr/master

Fixed problems moving tiles while layers (Game Over/You Win) are still on
Merge pull request #12 from jperedadnr/master

More adjustments in traverseGrid: removed sorting of TraverseX, TraverseY,
formatting
use of atomicinteger
Merge remote-tracking branch 'upstream/master'
simplifying ui code
Merge remote-tracking branch 'upstream/master'
Added SessionManager to save/restore session in a properties file.
Use 's' to save (if you have a good position) or 'r' to restore (when the game is over or in a bad position)
The file can be edited an used also to test some movements.
No cheating allowed!!