Add support for Non Session Manager API

It would allow MuseScore to participate in "Session" involving other applications (Synthesizer, Effects, sequencer, Ardour ...), everything being started, loaded, saved and stopped at once.

The Non Session Manager solution is described here: https://non.tuxfamily.org/wiki/Non%20Session%20Manager
- The API: http://non.tuxfamily.org/nsm/API.html
- Communication is done via OSC as described here: https://non.tuxfamily.org/wiki/OSC

Note that "Non-Session-Manager" is not the only application supporting this protocol, there is https://github.com/Houston4444/RaySession too.