Changes

SPIGOT-5732, SPIGOT-6387: Overhaul Hanging entities

- SPIGOT-5732: Fix issue with spawning leash hitches and painting, by using the right block faces

- SPIGOT-6387: Allow hanging entities to be spawned mid air

- Use randomize parameter to determine if a random painting should be chosen or not

- Return BlockFace self by leash hitches entity

- Throw a standardised exception when trying to set a BlockFace to a hanging entity which the entity does not support, instead of using BlockFace south or throwing a null pointer