fixed: a defect in wavefront_obj::write_to_obj_file()
updated: texture file pathnames
updated: C2DPrimitivesTest
updated: Graphics/fwd.hpp
updated: C2DPrimitiveRenderer and its derived classes

deleted: some of the legacy OpenGL code
The OpenGL 2D primitive renderer creates GLSL shaders to render the 2D primitive shapes when the user only specifies the texture and does not specify a shader.
added: comments
updated: 2D primitive classes
updated: C2DRectSetImpl_GL::Draw()