Hi,

This patch updates Zrythm to 0.8.156. 

I also added support for SDL2 (alternative audio backend to JACK) and
RtMidi (alternative MIDI backend to JACK) so Zrythm can be used without
JACK. SDL2 and RtMidi use ALSA and ALSA sequencer respectively, which
unlike JACK require no extra configuration to use them.

Thanks,
Alex