documents: Tidy up GDataDocumentsFeed a little
documents: Tidy up GDataDocumentsFeed a little

Pecisk/libgdata-gtasks,Distrotech/libgdata,Distrotech/libgdata,pwithnall/libgdata,Pecisk/libgdata-gtasks,Pecisk/libgdata-gtasks,Pecisk/libgdata,pwithnall/libgdata,Distrotech/libgdata,Pecisk/libgdata,GNOME/libgdata,Pecisk/libgdata