added file loader support( kinda sketchy right now)

added PNG file loader
added buffer reader/writer
fixed shader attribute to vertex array mapping (although it is fixed now-- doesn't make use of attribute names)
fixed render pipeline problems
added texture support (MeshElement now receives a vector of texture names for each texcoord)
moved VertexElementDescriptor to RendererUtils.h
passing resource manager shared pointer to renderer to bypass sending resources from user space when creating renderer resources
refactored code