Tested on 1.12.2. (may still work for older versions or 1.13, but try at your own risk)
Now prevents shift-click moving Undroppable items to other inventories.
Now closes inventory upon attempt of moving or shift-clicking items into another inventory.
Now prevents moving Undroppable items into unidentified inventories (e.g. Mule chests and other uncategorized inventories) and added option to disable this in config ("containers.unidentified")
