Add attributes denoting whether namespace was read from or has been written to an archive
Add attributes denoting whether namespace was read from or has been written to an archive

jonfoster/pyxb2,balanced/PyXB,pabigot/pyxb,jonfoster/pyxb2,pabigot/pyxb,jonfoster/pyxb-upstream-mirror,balanced/PyXB,jonfoster/pyxb-upstream-mirror,jonfoster/pyxb1,jonfoster/pyxb1,CantemoInternal/pyxb,jonfoster/pyxb-upstream-mirror,jonfoster/pyxb2,balanced/PyXB,CantemoInternal/pyxb,CantemoInternal/pyxb