Add test on Directory.Entries operation

In org.nuxeo.client.marshaller.NuxeoResponseConverter#convert we currently handle automation case, if entity-type is present in response.

We don't have a way to handle automation response without entity-type.
As automation can return a lot of different type, we can't leverage java typing and we need to deduce it from the response.

For instance the operation Directory.Entries/GetDirectoryEntries returns a json blob without entity-type.
We should fix Nuxeo server and then add tests on java client for such generic operations.