Unify ONManager, ScopeRegistry and OntologyScopeFactory implementations

To setup a scope, you have to:

1. get the ONManager
2. get the OntologyScopeFactory from the ONManager and use it to create the ontology scope
3. setUp() the scope
4. get the ScopeRegistry from the ONManager and use it to register the scope and activate it.

There is no point in having "unregistered" scopes, since their memory occupation is the same, so step 4 should be merged with Step 2. The developer or administrator should only be concerned with (de-)activating the scope.

At the same time, since the ONManager would become the scope registry, there is no need to delegate creation to a separate factory object, since its current implementation is not even an OSGi service component. This would reduce Step 2.

Solution: have ONManagerImpl implement the ScopeRegistry and OntologyScopeFactory interfaces as well. It could even be renamed to ScopeManager, in pair with the existing SessionManager.

It could also argued whether the setUp()/tearDown() method pair for OntologyScope is still useful.

Note that the API currently in place should only be deprecated, not removed yet, as there are already applications using it.