big ol' shop update

- Money now appears on the UI in the top right

- Added a shop. Now money isn't completely useless! WOWOW!!

- You can cycle through different potions by hitting tab

- You can buy potions from the new shop NPC (approach and press B to open the menu)

The shop is still a work in progress. It won't look the way it does in the final version, I'm just trying to get it functional first.