Pokemon Swarming

Redid how swarming hooks into pixelmon's spawning system to prevent concurrent modification and threading issues. It now creates a new tracking spawner per player. This does mean that swarm spawning has changed, now it is a capped # of spawns rather than a rarity multiplier or flat percentage.

This will lead to an increased number of spawns in the server, so be aware of that if that is a concern. The default is set to +20 pokemon spawns total in the world, shared between players, so shouldn't break the bank but also might not be super noticeable for 10+ people on the server in different swarm biomes.