Refactor high-level renderer

[Witek902]

• [ ] Ensure that renderer system is not using mesh/material/texture resource directly.
• [ ] Move the high-level renderer code to another project (e.g. nfRenderer):
  • nfCore/Renderer/ can be just moved
  • RendererSystem must be split into RenderSystem (wrapper for HL-renderer) and RenderScene (or something)
• [ ] Create "Demo" application for testing high-level features without nfCore (lights, shadows, meshes, post-process, etc.)
• [ ] Ideally, low-level renderer (backend) interface should not be visible by the nfCore/demo app.

The biggest problem will be to extract code from RendererSystem and View classes