Weapon FANCY kits

Based on a random idea I got while reading the forums.

Adds a handful of cosmetic weapon kits for weapons, such as gold
plating, silver plating, chrome plating, and a "bling" kit consisting of
diamond studded gold plating.

Works perfectly on weapons with shoulder straps, but I haven't figured
out how to make it work on holstered or wielded weapons.
Single, double, sawn-off, and R870 SGs all have grip slots despite probably not being pistol-gripped.  Shan't speak for Rivtech and since the L12 is based on the Neostead, I think it has one.  Easy enough to remove those slots in a merge.