Merge pull request #50 from lanice/nirvana_cleanup

Nirvana cleanup
add pausing of created sounds (fountainsound) when toggling physics pause. #40
adjust background sound volume. #40
replace for loop with c++11 range-based for loop. #40
fix CMakeLists order
Merge remote-tracking branch 'origin/nirvana_40' into nirvana_rendering_postprocessing_51
fix game shutdown #51