changes to collision detection

Hitbox now accepts any two vectors,
experimental directional detection
rewrite collision detection for Player

add detectTileCollisions to choose Tiles for checking
add collideWithTile which stops the player and bumps them backwards

remove unused methods from Player:
 - isAnyField
 - collisionWithField
remove unused definitions from Hitbox:
 - directional collidesWith
 - Side enum
 - Position enum