Create LeveledMobs17

Been working on some updates/fixes for this now that I have a bit of time.

* Lots of minor code clean up.
* Some of it's coding style/readability.
* Commented most of the code.
* Big changes:
** Levels are now in Metadata, so custom names are not vital
** Should not conflict with custom names from other plugins.
** Tested to work with MCMMO health bars and Infernal Mobs custom names.
** Works with name tags on leveled mobs.

Currently names mobs as "level # {mobtype}", but there is room to add some config options to that as well.

Commented out the metrics, as I don't have that package installed, just as I didn't want to mess with it right now.