tilemonster: centered window with a single map

instead of appending new maps to the body
tilemonster: fix a few crippling painter bugs

-holding both mouse buttons no longer instantiates a rogue interval
-redraw the whole map instead of just the painted tile
-highlighted tile no longer sticks when leaving the left or top edges
-got rid of some unnecessary/unused variables
tilemonster: double-clicking the map no longer tries to select text