Added initial PotionTypes and EntityTypes implementation.

In order to avoid duplicate entity names with mods, all entities will be stored in an internal registry as 'modid:name'. If you call EntityType.getByName(id)
and do not include the modid, it will assume 'minecraft:name'.

Potions currently do not have this feature but I plan on adding if needed.

* Added MixIn for EntityRegistry in order to catch mod entities and add
them to our internal registry.
Implemented Living Monsters.
Added license headers.
Implemented Living Animals.

* Implemented Living meta types.
* Implemented ItemStack.
* Updated SpongeAPI.
Implemented rest of Living animals.

* Implemented BiomeTypes.
* Cleaned up some mixin code.
Reorganized mixins to match API package structure.
Fixed wrong name in HorseVariant constant.
Merge pull request #82 from SpongePowered/impl/mcbasetypes

Initial implementation for entities, biomes, items, and potions.
Fixed various mixin errors when launching game.

* Cleaned up some code.
Hook up event listeners to Forge's event bus as well as FML's
Bump up API version.
Implement some missing changes in the latest API bump.
Fixed compilation.
update to latest forge
update forge once again
Migrating mixin functionality from Sponge to new project
Updated gitmodules to fix travis errors.
Implemented PlayerInteractEvent.
Initial implementation for Text API.
Use a union before setting text styles