Bring back more advanced Realtime rendering examples

[haraldsteinlechner]

There are some examples burried in src/Demo/Examples/* which did not make it into really nice examples in /src/Examples (netcore). There is some love needed. The good thing is that those demos are kind of cool realtime rendering tasks. Some ideas are:

• Shadow mapping, e.g. sketched here: https://github.com/aardvark-platform/aardvark.rendering/blob/master/src/Demo/Examples/Shadows.fs
• Shadow volumes
• Lighting, effects e.g. normal mapped scenes, postprocessing etc
• Deferred shading

Source of inspiration could also be found in the great aardvark.rendering based game samy the salmon by @hyazinthh and @gnufu

@luithefirst