TODO for the nearest future:
- Add abstractions for checks that might be done several times, such as pathname
  checks and try make it more generic than the current state.
- Add abstractions for executing queries or listing albums and tracks.
- Support other types than strings.
- Simplify scanning a bit a lot of code used multiple times.
- We should add filename path to database schema in case we want to touch the
  data :)
- Check for errors in mp3_list.
- Add proper debugging facilities.
- Support looking up a file and reading from it.