add scrobbler, rating, play counts and other functionalities to MPD

 mpdcron is a daemon that watches a Music Player Daemon instance for idle
 states and execs commands triggered by specific states.
 .
  * Uses mpd's idle mode.
  * Calls hooks depending on the event.
  * Sets special environment variables to pass data to the hooks.
  * Optional support for modules via GModule.
  * Included modules:
    - notification
      + uses notify-send to send notifications.
      + can detect repeated songs.
    - scrobbler
      + uses curl to submit songs to Last.fm or Libre.fm
    - stats
      + module saves song data to a sqlite database
      + supports loving, killing, rating and tagging songs, artists,
        albums and genres.
      + tracks play count of songs, artist, albums and genres.
      + implements a simple server protocol for remote clients to
        receive data.