Automatically load all Structures from a specific folder

[PssbleTrngle]

• [x] Specify a folder, from which every .nbt structure file automatically gets loaded
• [x] Don't register structure on error
• [x] subfolder of assets, allowing datapacks to simply add rooms
• [x] Optional .json File containing information like the weight and other generation conditions

Generation Conditions may include

• Weight
• Floor white & blacklist, negative numbers start counting from the top
• Above / Below other room (like portals?)
• Mod loaded