Add "Ignore colormask" override option for importer

[HiLordReilo]

As stated in the wiki:

Some materials are supposed to have overlays, but KKBP cannot tell when that’s supposed to happen, so it defaults to enabling overlays.

However, what if user knows there are no materials that have overlays or they just didn't use overlays? In that case it would've been nice to have an option to force "Ignore colormask" to 0 for materials on import to skip fixing white items.

[FlailingFog]

I thought this was a great idea, so I was going to add it in the next release, but I just found what was causing this.
It turns out that it was not an issue related to overlays at all. The colormask was supposed to be nonexistent for those materials, but the KKBP exporter was creating a color mask anyway, so that is what prompted the existence of the "Ignore colormask" slider.
The Ignore color mask slider will be removed in KKBP 8.0 and all clothes related to this issue should look correct out of the box.