Added support for custom mobs and added boss kills
Added support for any custom mob that fills in the customMobName. MythicMobs was tested but other custom mob plugins may work if they function similarly to MythicMobs. I allow you to configure a global custom mob stat with an optional prefxFilter to catch any custom mob otherwise I give you 10 custom mob sections to configure. See the config file documentation for more information on setting up stats for custom mobs.
Added Killed bosses stat line for Ender Dragon and Wither bosses.