Automatic Base Skinner

- Shift+Middle Mouse: Will cycle the target structures variant, if it exists.
- Middle Mouse/Left Shoulder: Will copy current variant. Use the Apply Variant mode on the tool to change an existing skins variant to the copied one. All modes that apply a skin will also apply the copied variant(Add Single, Add Multi, Automatic, etc).
- Added a toggle visibility option for skin entries. Hidden entries are hidden from the selection screen and will not be used when skinning.

- Note: Any of the bulk addition modes are throttled down(if necessary), if you have a variant copied. This is required to properly skin and then change the variant.