Hyper's Hexcast Addon

Just a little addon for HexCasting by Petrak@. Adds the following patterns: * Inclining Prfn: Get a list of integers within the Interval [0,n)) (equivalent to Python's `range`). * Rider's Prfn: Get the entity that a given entity is riding (e.g. a minecart). * Jockey's Prfn: Get a list of entities that are riding an entity. * Driver's Prfn: Return whether an entity is controlling the entity it's riding. * Mount spell: Cause an entity to begin riding another entity. * Dismount spell: Cause an entity to stop riding the entity its riding.