Can't create classes inheriting from node without explicitly importing rclpy.node.Node #156
Description
To settle on before tagging the release.
Since #147, all classes inheriting from rclpy.Node need to explicitly import rclpy.node.Node (see ros2/demos#196).
It would be great to allow users to use that class without having to explicitly import it as it was the case before.
@dirk-thomas could you provide more information about the need of delaying importing the singleton and the possible alternatives to restore previous usability?