nitdoc: Extend the model to help the importation from Doxygen.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
neo4j: Print an error message when the server is down.

Show the message as expected.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>