* The colored locked doors and the Electric Door are increased in size
to better match Boy's sprite size.
* Colored doors now have a "locked" and "unlocked" state when closed;
when locked, a gold padlock hangs on the door with a keyhole shaped to
match the corresponding Colored Key.
* Added initial walking sprites for the player character, "Boy."
* Player doodad filename and title screen level are now configurable in
the balance/numbers.go package.
