Inital release

Reloads hotbar.nbt when the "Saved Hotbars" tab is clicked.
Immediately after the CreativeInventoryScreen gets the Client's HotbarStorage, load() is called on the storage to reload from the file.
No changes to saving are implemented in this version, because that would require intercepting updates to HotbarStorageEntrys and somehow getting a load() back to the HotbarStorage, and I don't feel like doing that rn.