Update NEWS for 1.7.3 release
Update NEWS for 1.7.3 release

philipl/gvfs,gicmo/gvfs,xkahn/gvfs-cmis,cpatulea/gvfs,gicmo/gvfs,xkahn/gvfs-cmis,halfline/gvfs,halfline/gvfs,cpatulea/gvfs,xkahn/gvfs-cmis,xkahn/gvfs-cmis,halfline/gvfs,gicmo/gvfs,gicmo/gvfs,philipl/gvfs,philipl/gvfs