Fixed some game issues

Fixed:
- Clear all unwanted input from user's spamming, only keep the latest
one.
- Pacman now power up when eating power pellet, time is fix at 50 turns.
- Ghost killed by powered up pacman, return to spawn point and wait 50
turn to come back.
- Ghost will no longer clear small pellet, fruit and power pellet
characters.
- Refine collision code.
- Change some colour for easier to play the game.
- Each turn will last roughly 500 ms now, this time already included the
AIs calculation time and all other stuff.