HIDE cursor in fullscreen mode

Since right now we do not support toggling between windowed and
fullscreen mode, there is no code in place to eventually show the cursor
again.
DISABLE serializing listeners with C++ callback, as there is no way to
restore the callback when restoring the listener.
CLEANUP code.
RESTORED renderer that does not try to eliminate objects from render
queue and some small code optimizations.

For the test data, the older rendering approach is much faster than the
current default_renderer. It remains to be seen which one is best for a
real map.
FIXED memory leak
ADDED logic to skip rendering frames in order to keep game speed
constant.

Most of the code had been in place already, but now it looks and behaves
a bit more like a proper main game loop.