Improve class-level generic type parameters

[davejoyce]

Improve class-level generic type parameters, such that:

• NamespaceId<T> implements Versioned<NamespaceId<T>> or equivalent
• TemporalNamespaceId<T> implements Versioned<TemporalNamespaceId<T>> or equivalent
• BiTemporalNamespaceId<T> implements Versioned<BiTemporalNamespaceId<T>> or equivalent