Re-organize GUI and Polish Demo

[CaffeineViking]

After we're done with everything else we should clean up the GUI and polish the demo. Right now a lot of the functionality is immutable and we should add extra knobs to them so people can experiment with the method we have presented. There are a bunch of things that are still missing: changing hair parameter at runtime, modifying the light direction, adding *.vkhr files for the Cem Yuksel styles, simulation #17 (probably just plug-in TressFX), model rendering for the raytracer so both rasterizer / raytracer scenes match, texture support for the model rendering (so we don't get the white-spots, because our strands are pixel-sized, as done in the "new" Deus Ex), infinite white plane to get shadows in the scenes. More importantly!: move buttons into the correct "separators" and remove the now "unnecessary" buttons as they are confusing. None of these things should take long to fix (maybe combined they can take 1-2 days), but I just haven't gotten around to doing any of this yet.

Also general documentation of the project, including documenting the shaders and the more important parts of the renderer (the wrapper will probably be refactored into a separate project later after the thesis).

Not a priority for now, but I want to keep this here so I remember to fix these things at a later point in time.

In fact, let's make a list:

• Knobs for changing hair style parameters (diffuse / specular color and shininess) at run-time.
• Changing light direction via the GUI (not possible right now, only the "color").
• Add Cem Yuksel hair style scene files.
• Crawl scenes for any new files, and also add the vkhr scene given via the CLI.
• Add mesh rendering to the raytracer as well, so we can have more-or-less the same scenes.
• Add white plane below the hair style for all built-in vkhr scenes to demonstrate shadows.
• Add simulation Implement a Simulation Pass #17 running in compute e.g. via TressFX (left as future work).
• Texture support for have the same results as TressFX 3.1, and remove the "white spots" too.
• Re-organize the entire GUI to make more sense and allow people to change the parameters.
• Add way to visualize the light sources (e.g. via Billboard). (isn't needed :-P)