Worked on making a unified debug message callback system for renderer system.

Renderer is more or less ready to be moved into own repository.
Decoupled Asset system from renderer.
Made a Renderer::MeshDocument struct for importing meshes.
Renamed some Renderer::CreateInfo structs to InitInfo.
Current version does NOT work. Asset manager needs more work.

Signed-off-by: Nils Petter Skålerud <np_skalerud@hotmail.com>