Embryo of a new control assignment system
See controls.py for a short documentation

/!\ some logs are not disabled
More advanced version of controls management
Handles all former possible controls

/!\ possible memory leak
Added unbind function to delete control assignation
Some minor corrections
"End" of branch (minor modifications)
minor changes (shield control set as example)
Controls are dictionaries. Keys: 'name', 'player', 'event_type', 'event_params'
Missile speed and initial direction changed
Some changes to the Key Control system and to the missile trajectory (tried an implementation of a double trajectory)
Still nothing concerning the menu !