New Feature class

A new class Feature is defined as superclass of FeatureKind and FeatureOfInterest.

A FeatureKind is a model (from its definition) and a FeatureOfInterest is a real-world entity. They are totally different things: the former refers to an abstract thing and the latter refers to a physical thing.

Any individual that is an instance of FeatureOfInterest (or of a FeatureKind) will also be an instance of a Feature, so it will be something both abstract and physical, which is not the intended representation.

Also, it will give problems when aligning to any top-level ontology.

And it will be confusing for users of SAREF to have three different classes in order to represent features.

And, even if we state in the documentation that it is an abstract class, people will instantiate the class sooner or later.