#2838 collection handling partially fixed (now can handle tins and doesn't output bogus gml output

git-svn-id: http://svn.osgeo.org/postgis/trunk@12825 b70326c6-7e19-0410-871a-916f4a2858ee
Share code handling field name mapping between loader and dumper

git-svn-id: http://svn.osgeo.org/postgis/trunk@12826 b70326c6-7e19-0410-871a-916f4a2858ee