Fix bug in local request dispatcher (unable to dispatch request-only requests)

Also refactor the unit tests for the request dispatchers, using proper mocks
this time instead of stub objects.
Improvement to the service layer request interface plus new extension method

This now makes it possible to dispatch strongly-typed service layer requests
and receive their strongly-typed responses, without needing to use generic
method signatures.
Bump version numbers
Merge branch 'release-2.3.0' into production
Merge branch 'production'