4.7.0

Added early support for shaders! (Finally...)

• Use the new PixelShaderMeta record to specify a shader to load
  • As with all other assets, the shader must be added to your project's Content.mgcb
• Use GraphicsManager.SetPostProcessingPixelShader(...) to set a shader to apply to the entire screen; pass null to clear the shader again

More uses will be added in future releases!