Include upgrade instructions for installations based on ansible script (copied from docs/installation/index.rst)

See #852: improved routing logic for federation messages (support multiple objects types for one route)

See #261: Added a rate-limiting (throttling system) to limit the number of requests handled per user/IP

Added "refresh=true" API param to artist, track and album detail to retrieve up-to-date data if needed

- Use `useradd` features to simplify user creation:
  - `-U` creates a user group,
  - `-G docker` adds the user to the `docker` group
- Document available versions and their usage
- Use `chmod 0600` before editing the file!
- Use `cat` instead of multiple `echo`es
- Comment all lines in `.env`
- Use `${FUNKWHALE_VERSION}` where applicable instead of `|version|` to
enable copy-pasting more commands

Moved incorrect paragraphs

Added link to mopidy-subidy

Fix #781: Added a `check_inplace_files` management command to remove purge the database from references to in-place imported files that don't exist on disk anymore