Fix #706: Added a 'fix_federation_ids' management command to deal with...

Closes #706 (closed)

Example usage:

python manage.py fix_federation_ids https://node42 https://node1 --no-dry-run --no-input

Will replace 108 found occurences of 'https://node42' by 'https://node1':

- 20 music.Artist
- 13 music.Album
- 39 music.Track
- 31 music.Upload
- 1 music.Library
- 4 federation.Actor
- 0 federation.Activity
- 0 federation.Follow
- 0 federation.LibraryFollow

Replacing on 20 music.Artist…
Replacing on 13 music.Album…
Replacing on 39 music.Track…
Replacing on 31 music.Upload…
Replacing on 1 music.Library…
Replacing on 4 federation.Actor…
Replacing on 0 federation.Activity…
Replacing on 0 federation.Follow…
Replacing on 0 federation.LibraryFollow…

cc @OniriCorpe