tracker: Populate track number metadata
tracker: Populate track number metadata

https://bugzilla.gnome.org/show_bug.cgi?id=753732

grilofw/grilo-plugins,grilofw/grilo-plugins,jasuarez/grilo-plugins,GNOME/grilo-plugins,MikePetullo/grilo-plugins,GNOME/grilo-plugins,MikePetullo/grilo-plugins,jasuarez/grilo-plugins,MikePetullo/grilo-plugins