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 crash when opening BigTestMap.
fixes #385
Merge pull request #387 from hwoarangmy/development

Fixed crash when opening BigTestMap.
Merge pull request #388 from akien-mga/development

Fix library tooltip and balance Greed or Might
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
Fix doc installation