New color selector user control

Unfortunately, this is not a full-blown "color selector".  This is
simply a thin user control to replace the picture boxes I was previously
using for color selection on tool dialogs.

The advantage of a user control (besides less copy/paste code throughout
the project) is that it interacts nicely with the new Command Bar.  The
color selector can be easily reset, randomized, and saved/loaded as a
preset.
Fix command bar to work with control arrays

If a control is part of a control array, we can't simply store its name,
as it shares that same name with other control!  We must also store its
index, then retrieve that index at read time.

Also fixes a bug with resetting according the Min property of certain
controls
Add command bar to monochrome conversion tool

This was my testing ground for the new color picker interaction.  Seems
to work just fine.