initial attempt at undecorating tiled windows
split undecoration into two prefs undecorate-tiles and undecorate-mode, to allow for toggling on/off without altering the mode
Reduce chances of surprises when removing windows. Didn't fix the infinite loop problem though.
Removed UNTILE_MODE - removing *all* decorations is just too buggy,
and it's unlikely to be used by many.
Fix some minor bugs in undecorate code.
Merge branch 'undecorate'