big ones
- add support for external analysis tools to provide arbitrary tags for the index
- add example tools for detecting bpm and melodic key
- add range-search (duration/bpm/key/... between min/max values)
- hotkeys for changing songs + skipping
0..9=jump,J/L=file,U/O=10sec,K/I=folder,P=parent
the rest
- add search timeouts and rate-control on both server/client-side
- add time markers in the audio player
- remember the file browser sort order
- the initial html retains server order, so use the tree to navigate
- fix a race in the tag parser when using the multithreaded FFprobe backend
- fix minor stuff related to volume flags and tag-display options
- repacker should no longer break the bundled jinja2