Add a way to change entity max health

Add the ability to change the max health of an entity.
This time with less base edits.

Usage:
ForgeHooks.setEntityHealth(String entity, int health);
entity is the class name without "Entity" and ".class"

For wolfs there is "Wolf" and "Wolf Tamed" and for slimes "Slime1", "Slime2"  and "Slime4". (Also for MagmaCube)