Removed the HLSL and GLSLES folders.

The Cg/ one is needed on Windows if we're not using the Cg plugin.
And the GLSL and GLSL150 can be used depending on the hardware used AFAIK.
Removed the need of @OPENDUNGEONS_MEDIA_DIR@ + misc things.

I also added the missing octree debug plugin and remove various useless lines.

Part of #367
Actually fixed setting the game data path and version when using MSVC.

The last time, my cache flawed my tests.

I also made sure to display Cmake Cxx flags correctly when on MSVC.