Optimize memory usage in ChipTuneEngine.

[razterizer]

Optimize memory usage in ChipTuneEngine so that instead of generating all waveforms per note first and then playing them, instead we create a waveform one or a few notes or beats before it is about to be played and then freeing up the memory just as a note has finished playing.

[razterizer]

Optionally group together sounds that are identical for more efficient memory usage. You can use pointers or something.