Added musly_jukebox_gettrackids() API
Add musly_jukebox_tostream/fromstream
Update selftest to use musly_jukebox_tostream/fromstream
Update command line client to use musly_jukebox_tostream/fromstream and update instead of recompute jukeboxe files given with -j/-J when possible
Update README to reflect API extension
Regenerated documentation to reflect API extension