Add custom model data, item type, and lore options to MythicMob spawn eggs

Summary

Add custom model data, item type, and lore options for MythicMob spawn eggs.

Usage

It would allow for custom textures and different items for spawn eggs. The ability to write lore for the eggs could bring more story into a boss, help describe its difficulty, etc.

Value

A nice cosmetic option.

Priority

Medium, since it's a cosmetic thing. But it'd be a really nice touch.

Implementation

In the mob file under options.