Upgrade buildings in place!

Press (U) or whatever you rebind it to while hovering over a building to attempt upgrading it.

If you have the next building in your inventory, it will replace instantly and if not it will begin crafting if materials are present while marking it with an icon.

If you don't have the item or stuff to craft it, nothing will happen

Upcoming features:

• If a upgrade requires the predecessor to craft (yellow belt -> red belt) return a temporary belt just for crafting
• Beter ways to detect cancelling of upgrades
• Shift-U on belt to upgrade entire line?
• Upgrade based on predefined upgrade planner
• Notification if the player doesn't have the materials
• Better keybind (u is so far away from wasd)