Fix inappropriate requirement that complexType be non-empty; change default to common case
Fix inappropriate requirement that complexType be non-empty; change default to common case

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