Fixed a bug with item loading.

You're supposed to be able to only list the altered stats
with equipment, and that didn't work before, so I fixed it.
Added details to items.
Added popup helper functions and detail buttons.

Popup helper functions come in the form of AnnoyingPopup (name
subject to change), and were integrated in the InventoryMenu
and ShopMenu classes. Also added to these classes were item
detail buttons.