Cleanup pallette

[DOS386]

Maybe the time is NOT ideal to post suggestions by now, ... but
related to my bug report:

http://newsgroup.xnview.com/viewtopic.php?t=10794

I suggest following feature:

Cleanup Pallette

It should:

- Remove unused colours from the pallette (after cutting for ex.)
- Reduce duplicate and multiplicate colours to 1 (after manual editing them)
- Sort the colours by brightness (start with black, end with white, as long as present at all)

[Hobbe]

Seconded

And being able to open and edit a palette file without actually opening an image, would be nice as well.