Songbird 1.9 compatibility.

* Bug #80: The wrong song gets notified if the PartyRuffle add-on is used
* Feature #11: Global shortcut to show notification window
* Feature #108: Possibility to disable animation

* Bug #42: Add compatibility for Songbird 1.8

Have a look into the preferences dialog for the new features:

    * Bug #8: Remove listener on unload
    * Feature #9: Add possibility to change notification location
    * Feature #10: An easy ability to turn off automatic notification without restarting Songbird
    * Feature #12: Friendlier icon (white gradient)
    * Feature #37: Code Cleanup

* FIXED #0000001: Hide notification after threshold of next song, even if next song is unrated.
* Notification now gets updated when metadata of shown song changes.
* Notification now also closes when song is rated in mainplayer.

* Renamed extension to "Rate Your Library" since there is already an extension and service with the same name.
* FIX: Don't reopen notification for the same song.
* Removed "Rate Your Music - Unrated Song" headline in notification.
* FIX: Scale albumart.

First release of the extension. Feel free to leave any comment, bug reports, etc. - please!

NOTE: This is the first release, so treat it as an alpha version that may contain bugs!