[WFS-Docs] Document gml_featureid metadata in WFS howto

[dmorissette]

In bug 1413, Steve added Steve added the ability to use a "gml_featureid"
metadata to specify a feature id field for WFS services which is output as
gml:id in the GML responses.

This needs to be documented in the WFS server howto.

Also, I'd suggest that you keep an eye on bug 1759 as this feature may need to
change a little bit to be made WFS 1.0.0-compatible.

[nsavard@…]

I think this bug should be fixed for the next release.  We should add a note for
wfs_featureid and ows_featureid as well.  What do you think?

[dmorissette]

Setting 4.10 release target milestone

[jmckenna@…]

added reference to "gml_featureid" and "wfs_featureid" to wfs-server doc
(http://mapserver.gis.umn.edu/docs/howto/wfs_server)