Can now unwear items, fix inventory bug

Fix bug : worn items weren't saved/loaded correctly, and we would end up
reading garbage.

Can now unwear items (right click on one of the 8 slots around the pony
in the inventory). Still can't wear items properly, tho.
Can now parse Items.xml and build an item DB

We need to know the wearable positions of every item, so we can send
correct Wear Item Requests and check server-side what we're trying to
wear and where it should go;
Can now wear items properly

But we can't unwear anymore, since the items you wear don't appear in
the worn slots in the inventory!