first mostly-working build supporting GTK rethemeing via the Theme Manager
revert UIConfiguration back to a normal member of ARDOUR_UI
big strides in color management
fix default gtk background color
remove debug output
fix up a logic problem when editing palette colors
remove all explicit button text colors; use contrasting_text_color() instead.

Also, use a slightly off-white rather than pure white, which should really be configurable
fix up various issues with UIConfiguration, saving state, RC file loading etc.
remove stacktrace
the return of correct audio meter colors
remove old alias names for meter fills from default_ui_config
sane audio meter default colors
new code-level defaults for audio peak meter colors
Revert "new code-level defaults for audio peak meter colors"

This reverts commit 564d2860f85340ea091cfa4d92cb5f84d2a40fb1.
new code-level defaults for audio peak meter colors
Fix shift-rect-select with MIDI notes.
Fix and simplify step_mouse_mode.
Unify gain and draw tools.

There might be a few special cases lingering around from attempts at magic tool
business, but this seems to work fine as far as I can tell.
Draw region automation with draw in either mode.

Perhaps debatable if contents should be edited when not in internal mode
whatsoever, but consistent with audio region gain and track automation.  It's
less of a problem with the draw tool than, say, object since drawing stuff is
its entire purpose.
Fix uninitialized value in note create drag.