Nether Mooshrooms

Adds new varieties of mooshrooms adapted to the conditions of the Nether to the game. These creatures come in two variants - crimson and warped, which completely replicate the behavior and mechanics of their ordinary counterparts from the Overworld.
Both types of Nether mooshrooms are attracted to and breed with nether wart. An interesting feature is the ability to transform the mob - if you feed the crimson variety a warped fungus or vice versa, the cow will change its appearance to the opposite type.
