This also refactors the panel button code to rely less on WPF bindings.
They just get in the way for anything nontrivial. Doing it this way
lets us treat the panel buttons as an interface for setting colors, to
handle the different fields that are set for the panel colors and floor
color.
This fixes the default always being up-left (which is usually disabled),
causing the color slider to not do anything until you select a different
panel.
Glenn Maynard