[Bf-committers] Convert "Bone Color Sets" to a bit more generic "Color Sets"

[Gaia]

Hi;

In the theme editor we have "Bone Color Sets" which currently are only 
used for bone groups.
I'd like to propose a few minor changes:

1.) Rename the section in the User Preferences from "Bone Color Sets" to 
"Color Sets"
Reason: I think we can (re)use these color sets for other contexts as 
well. There seems to be no reason to tag them to bones only.

2.) Make the Set names editable, so that they could be named theme 
dependent. For the default theme i propose:

Color Set 1  : Red
Color Set 2  : Orange
Color Set 3  : Green
Color Set 4  : Blue
Color Set 5  : Muted Red
Color Set 6  : Violet
Color Set 7  : Muted green
Color Set 8  : Grey green
Color Set 9  : Yellow
Color Set 10: Dark grey
Color Set 11: Pink
Color Set 12: Grass green
Color Set 13: Light grey
Color Set 14: Brown
Color Set 15: Dark green
Color Set 16: custom-1
Color Set 17: custom-2
Color Set 18: custom-3
Color Set 19: custom-4
Color Set 20: custom-5

hmm, actually some slight reordering would be appreciated as well, e.g. 
place red and muted red below each other, etc...

3.) Allow to add custom defined sets. Actually we could remove the last 
5 Color Sets from the default theme, and add the ability to create color 
sets as needed by the theme.