[Enchantment] Use setSpawnFlags() to control monster spawning

[MarioG1]

At the moment you just cancel the spawn events of mobs/animals to control mob/animal spawning. A much better way is to use setSpawnFlags(boolean allowMonsters, boolean allowAnimals) to disable/enable monster and animals pawning.

This will also fix #1424 in an better way. The gamerule doMobSpawning prevents all mobs (animals and monsters) from spawning.

[MarioG1]

@dumptruckman @FernFerret you should look into the PropertyValidator's in MVWorld.java because the are never called which leads to some problems/not working foundations.

[FlippantCactus]

If you have a suggestion about spawning mobs, by all means, make pull request.

[dumptruckman]

The current spawn control is somewhat of a mess. The future of multiverse likely does not include individual mob type control and will use the more efficient means available in bukkit. If you want to make a PR updating this feature, please do.