replace nzbget with sabnzbd

[AntonyLeons]

addresses deprecation issue #84

minor issue that the default port for sabnzbd is 8080, a popular port on most servers

[ynazar1]

The PR is missing:

• Instructions on setting up the sabnzbd (and removing nzbget) as well as any integrations/hooks that are needed to happen in the *arrs
• (As mentioned above) sabnzbd runs on port 8080 by default and this needs to be worked around by mapping it to different port in the docker compose to avoid port conflicts as well as updating documentation and docker compose config to reflect that

[ynazar1]

Slightly better docker-compose avoiding port conflicts. Use /data/downloads/whatever inside the container when setting up directories under config options.

  sabnzbd:
    container_name: sabnzbd
    image: lscr.io/linuxserver/sabnzbd:latest
    restart: unless-stopped
    # network_mode: host # Cannot use 'host' if remapping ports
    environment:
      - PUID=${PUID} # default user id, defined in .env
      - PGID=${PGID} # default group id, defined in .env
      - TZ=${TZ} # timezone, defined in .env
    volumes:
      - ${ROOT}/downloads:/data/downloads # main downloads folder for everything
      - ${CONF_ROOT}/config/sabnzbd:/config # config file location
    ports:
      - 6789:8080 # Remap port for sabnzbd (usenet client) use old nzbget port