optimize compilation process

[dixx]

For convenient compiling/running/debugging of the project, we need to think about:

• a method to automatically link the project to local Irrlicht/IrrKlang lib folders (e.G. via environmental variables)
• a cross-platform make file (CMake was introduced by mbrendler)
• a method to copy necessary media files and lib files to the output folder
• a method to have tests in the same or another project

[dixx]

CMake provides most of the wanted features, so let's use it.