Updated model loader to handle multiple attr sets

Updated model loader to handle multiple attr sets

Modified GLTF parser for attributes to create attribute sets
for joints/weights/texcoords/colors

Added macro definitions to ShaderOptions, fixed hash to account for
macro/def strings.

Changed shader manager to create shader with extra attributes

Change-Id: Iabe2772eaf767ca3055dd415752c5a612942f0a4