FirEmerald's Block/Item model API

Adds in the ability to use Block and Item models from code, like before 1.8.

It's used FAIRLY similar to the formats in 1.7.10 - You create you renderer, and register an instance of it with the Block/Item of your choosing.
Item renderers should be able to be ported with only a few tweaks, but block models must now be done using the VertexBuffer functions. You can find some helper methods in RenderUtils that you can use and learn from.

There are 2 example renderers at the API source.

One is a block renderer that recreates MOST of the render code for grass, saving the coloring of the item form and any sort of smooth lighting and ambient occlusion. I'll update it with those if I ever figure out how to make them work.

The other is an item renderer ported from my Metroid Cubed 3 mod. It replaces the bow model when held with the powerbeam, complete with charging animation except for the energy bit at the front. It shows how you can tell if the item is being held in the left or right hand of the client player, and how to render an item using those models generated by utilities such as Techne and Tabula.

It is my hope that this coremod and API will help re-spark interest in modding for 1.10.2 and beyond.