FCPInterface: Send versionID of EventSource implementors
FCPClientReferenceImplementation: Parse versionID of
Identity/Trust/Score

Fixes Subscription synchronization not working: The versionID of the
objects of the synchronization would be different to what is sent in
BeginSynchronizationNotification / EndSynchronizationNotification,
resulting in the client deleting all objects part of the synchronization
because they looked like they had an obsolete version ID.
FCPClientReferenceImplementation: Fix bogus boolean logic in assert

The intention behind the assert is: It should succeed if the
subscription does not exist already. If the subscription exists already,
it must not fail if the errorCode is SubscriptionExistsAlready, because
that tells us that it may exist already.