Added Mob Cannon Feature

/launchmob (/launch, /lmob, /lm) [mob name (optional)]

Base command permission: mvpgadgets.launchmob
All command permissions: mvpgadgets.launchmob.*
All per-mob launch permission: mvpgadgets.launchmob.all
Per-mob launch permssions: mvpgadgets.launchmob.<mob_name> (all lower case)
Random mob launch permission: mvpgadgets.launchmob.random

All features are 100% tested and debugged. :) (And removing snow golem trails were the death of me!)