Gamerule to stop endermite spawning

Add a new gamerule called something like "doEndermiteSpawning" that, when set to false, will prevent endermites from spawning from an ender pearl.

I personally find endermites to be annoying and I would use this gamerule. This gamerule would also fit with the currently existing 'doPatrolSpawning', 'doTraderSpawning', 'doMobSpawning', and 'doInsomnia' gamerules.