New COOP mode

In order to please some japanese guy who refunded the game, we decided to introduce a new game mode: coop! You can now play with your firends against two extremely well coordinated AI. Will your teamwork and friendship be stronger than a stone cold machine? Let's figure that out. As per usual, we changed a lot of things in order to make the gameplay more interesting. Most of these changes were thought by our main (and only) contributor, Le Jo (thanks man): [list] [*] Added Coop mode [*] Prevented players from bumping after a smash: this does not seem like much but it means that smashing the ball will [u]not[/u] be safe anymore: any counter will be fatal. [*] Shortened the time where the ball is off limit. [*] Accelerated the game by 8%. [*] Backgrounds are now randomly chosen at start and do not change. [*] The sound that signals a fault is now played when the ball touches the ground. [*] Adapted the freeze time on smashes to smash intensities. [*] Fixed some sound balance issues. [*] Lowered dash distance [/list]