more cleanup of input handling.  It works, but is still not technically
correct/proper.  Need to synch pos with input state on server, and do
server-side corrections for other clients when input is received (rewind
buffer on server, apply input, replay number of missed input steps)
bit more work on input - attempting to allow multipart motion handling,
not working quite as intended.  Might need to do own movement calc using
OBB and let interaction / hit detection stuff use multipart code.