Player animation bug

The thing in default/player.lua was causing a crash if anyone used a
player model besides character.x. kaeza said they also needed a way to
register animations for models. (an animation being constants for a
finite state machine inside the model, which cannot be introspected
from the model?) So now it assumes the character.x animation is the
right constants for all models, except those who have an animation
registered, instead of crashing for all models besides character.x