Update src/metadata.json.in

Add support for g-s 3.7.3
Update the status text on play status

If the same song is stopped and played and
the client doesn't refresh the metadata property
the status text would stay empty.
Limit the _setStatus wait to known-bad players

Only Banshee is affected; other players send signals correctly.

Ref #111
Fix metadata remaining invisible on startup

Need to find a better solution though

Ref #111
Add Banshee workaround on Metadata change too

Closes #111
Merge pull request #109 from peutch/master

Add support for g-s 3.7.3
readme: Tested with GNOME-Mplayer, KDE's JuK and Dragon players