Flax collision detection ported to inform 7 style

inform7.py

@Walk.check(Solid)
def cant_walk_through_solid_objects(event, _):
    event.cancel()


@Walk.check(DoorPhysics)
def cant_walk_through_closed_doors(event, _):
    if not IOpenable(event.target).open:
        event.cancel()


@Walk.perform(Physics)
def do_walk(event, _):
    event.world.current_map.move(event.actor, event.target.position)