[DEV] A New UI for Scrolls of Upgrade

Continuing the trend of interface improvements coming to Shattered Pixel Dungeon in the next update, I'm adding a new window when you try to upgrade items!

Currently the only way to know how the stats of an item change with upgrading is to actually spend an upgrade scroll, but with this new interface you'll get a helpful little summary first! The window includes almost every stat in the game that scales with item level.