New ArcSDE featuretypes aren't compatible with their default output

Steps to reproduce:

1) Have a table in ArcSDE with an ArcSDE-managed ROWID column. For instance, create a featureclass in ArcSDE with ArcMAP.
2) Connect with geoserver and create a featuretype based on this featureclass
3) Note that the created featuretype schema includes the OBJECTID attribute.
4) Fetch an actual feature with that typeName from the wfs
5) Note that the OBJECTID (or other ROWID column) isn't present in the output, but is present in the schema. This means that the response isn't valid, and can't be.

This probably depends on the FIDMapper and some thinking about how Geoserver/geotools should handle ArcSDE featuretypes and their rowid columns.