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.
Added missing licensing info for the Defender.

Thanks to Danimal for pointing out. :)
Removed the GLSL150 folder and path in resources. Readded the Cg resource path.
Fixed a typo and added a warning about using local data.

Thanks to @akien-mga for pointing out.

Part of #383
Added a first version of a new skirmish map.
Made the creature spawner rooms taken in account in the kill all enemies objective.
Fixed the kill all enemies objective title to talk also about portals and temples.
Improved a bit the Bridge map.
Merge pull request #377 from Bertram25/development

Working on fixing #367 + misc stuff