Naming convention for exporting color attributes and UV maps

[alexguirre]

Currently, Sollumz exports vertex Colour0-1 and TexCoord0-7 based on the order the color attributes and UV maps are in. This is a common cause for issues on export (e.g. colour0 and colour1 swapped) and Blender doesn't provide an easy way to re-order them (afaik).

Having specific names to use for color attributes and UV maps to be exported should be less prone to errors.

[alexguirre]

Note, we are already using specific UV map and color attributes names for rendering, in the material node trees (e6642f8).

Should probably add a button below the UV maps and color attributes lists to rename them based on order, so users don't need to type the name for every single UV map and color attribute they create.