"Balance of Tris" 1st post Jam version

ChangeLog:

• Moved Elevator in the center of the screen.
• Greatly enlarged click/touch zone to select piece (nearly full screen width). 
• Challenge mode: If a piece is removed from an elevator below the others, the ones above it go back down.
• Added play time on bottom left of the screen.
• Changed set of pieces:
  • Level 0 : all the simple pieces (lines, cubes, L ...).
  • Level 1 : add light pieces.
  • Level 2 : add heavy pieces.
  • Level 3 and beyond: add 2 new pieces per level
• Added latest and best player score on main menu in both modes.
• Added online leader-board.
• Added a "reset profile" button