Proper color management support

[portnov]

For now, palette editor actually always works with 8-bit (s)RGB colors. It can read CMYK data in some cases, but it is just translated into RGB right away.

It would be nice to have:

• support of other color models (CMYK, Lab, LCh at least) for loading and saving colors
• support of color profiles (to know the color space in which RGB or CMYK numbers are expressed, and to know display profile to show colors properly)

Of supported palette formats, only Krita's KPL knows about these features. Scribus's XML knows about CMYK, but does not know about profiles.

I'm not an expert in color management at all, so I do not expect this to be done any soon. Just putting it here in case anyone wants to help.