[GEOT-4713] Add support for citext data in the postgis data store

This change allows the citext type to be used in features, allowing indexed case
insensitive queries. There probably could be better handling for extension types
in general for the PostGISDialect, but I'm not entirely sure what that design
would be, so I just followed the pattern set by the uuid type.
GEOT-4603 added NO_FEATURE_BOUNDS flag support to WFS 2.0 FeatureCollectionTypeBinding
[GEOT-4717] Have WFS 2.0 collection binding encode a valid numberMatched regardless of the field contents
Fixes #GEOT-4720

FeatureJSON#readFeatureCollectionSchema was adding a duplicate geometry
Binding now defaults to String if it cannot be determined (e.g. when all values of an attribute are NULL)