Visual Gear Overhaul

This fixes all overlapping gear graphics issues, and, by establishing an official layer system, it also allows circlets and ivy circlets to be worn over masks and helmets. They look perfect with every mask and helmet combination, except shrunken head masks, which cannot be combined with other headgear.

This will let you use pants and skirts at the same time as robes without issues. It will also let you equip, for example, a helmet and a circlet, or a mask and a circlet. Masks and helmets are layer 0, while circlets of both types are layer 1. This is to allow greater range of content in terms of style - formerly, using a mask came at the painful cost of being without a circlet or ivy circlet. That is no longer the case.

If need be, helmets can be balanced on their own merits. They already come with a spellpower penalty, and they don't do very much, so they are not as ubiquitous as circlets and ivy circlets.

I've also simplified armor equipping code, so future contributors will find it all in one place, rather than scattered around throughout the class structure. The layer system will allow us to add new armor items without any graphical trouble.

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Part 2

You can now switch between a weapon + shield, a shield, a bow, and a
lute seamlessly, even with a soldier shield equipped. **You can now equip
a different shield while soldiering**, and sling your soldier shield on
your back appropriately.

Yes, you can equip an Orc Shield or a Herald Shield and sling your
soldier shield on your back. You will use only the appropriate shield
for blocking. Soldier Shields will still give their rank effects and armor (you
do have a giant shield on your back, after all). 

Small round shields, gold shields, and knight's shields also work.
I expect we'll want to give the shield system a look, given that most
shields are silly useless.

Running around with all these gear improvements, I felt extremely stylish.
It was fun to wear a mask + circlet, and use a hammer + orc shield with
a soldier shield slung on my back. Meanwhile, I had grey shirt and pants
on under my Qor robes with no conflict or arm/leg glitches.
 
I felt like an Old Fashioned Qor Mage for the first time in years.
Do you remember when Qors used Orc Shields?
Pepperidge Gar remembers.