Add clean_library command

This adds a clean_library command to manage.py that will scan for deleted
files and offer to remove them from the database, and then offer to remove
tracks with no associated files as well as empty albums and empty artists.

Fixes #362.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
8 jobs for clean-library in 5 minutes and 10 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Review
manual #9400
funkwhale-review allowed to fail manual
review_docs
manual #9398
funkwhale-review allowed to fail manual
review_front
manual #9401
funkwhale-review allowed to fail manual
stop_docs_review
manual #9399
funkwhale-review allowed to fail manual
stop_front_review
 
  Lint
passed #9402
black

00:00:27

passed #9403
flake8

00:00:21

 
  Test
passed #9404
docker
test_api

00:04:43

passed #9405
docker
test_front

00:00:49