fix editing of nested/group item colors in theme manager
Fix marker bars "gradient" colors.
Fix control point colors.
Various color tweaks.

This commit changes some color names, nuke your theme.  This isn't quite ideal
yet, but takes some steps towards where I think things should go aesthetically:

Make automation tracks/regions colors correspond to their parent's type.

Make selected MIDI notes outlined in red like most everything else, and scrap
separate min/mid/max fill colors for selected MIDI notes.

Color automation ghost MIDI notes based on original note color.

Try to kill 90's looking brightish gray gradients in general.
add new parameter for minimum value of any range location
use new parameter to limit minimum length of any range location
Fix crash if new tempo is set to start at bar #0
Fix crash if new tempo is set to start at bar #0 / Follow-up for non movable tempos
Fix crash if new tempo is set to start at bar #0 / Follow-up for non movable meters