Adds the ground work for geometry shaders
Expands shaderData and gfxShader to allow for more shader types
note: when building a GFXShader in source you have to call setShaderStageFile with the shaderStage and the filepath for that stage.
Once we add compute shaders this will become more apparent as compute shaders are a stage of their own and do not require vertex and pixel files whereas other shaders sometimes do.
