[TEST] CleanUp 01

Experimental clean up.

(All changed/removed files are also stored locally)

Changelog Part 1 - Removed Folders
- /Assets/Legacy/ removed
- /Assets/Level/Demos/ removed
- /Assets/Level/Prototype/ removed
- /Assets/levels/ removed
- /Assets/middleware/ removed
- /Assets/Sound/music/ removed

Changelog Part 2 - Created Directories
- /Assets/scripts/debug/ created

Changelog Part 3 - Moved Files
- Assets/scripts/player/FPSCounter.cs moved to ./debug
- Assets/scripts/player/TestOptionen.cs moved to ./debug