Trackfs

feat(trackfs): Support WAVE files with accompanying cue-sheets (gh-8) (11)

To introduce WAVE support a few breaking changes got introduced:
- New naming scheme for virtual files; in case you have indexed the virtual
filesystem in some media-server you have to re-index it
- parameter `keep-flac-cue` got renamed to `keep-album`
- parameter `extension` now has to be a regular expression
- trackfs now also uses album meta-data from the cue-sheet to backfill
missing entries in the album file
- basic support for album-art in accompanying jpg files

* fix(flacinfo): escape tags for flac arguments

Special characters in tags, esp. title can cause invalid flac parameters when extracting a trackfs/cuesheet.
refactor(cuesheet): Major refactoring of cuesheet parser and support for album metadata.

* feat(albuminfo): backfill missing album tags from cuesheet

Renamed flacinfo to albmuminfo to perpare pending wav support.
Use cuesheet albuminfo in case flac file has not album metadata.

In case the flac file doesn't have an embedded cue-sheet, trackfs scans the directory for a file with the same basename and ".cue"-extension and reads it as cue-sheet.

Additional additions

- return accurate file size for track when already extracted in cache
- bugfix for concurrent reads