Forward gazebo contact point information

[ndehio]

Gazebo provides information about robot-environment contact points and corresponding forces via its own interface.
It would be beneficial to forward this information though our realtime-safe ports with realtime-safe types for automatic access in orocos-components.

[ndehio]

I implemented this feature in https://github.com/cogimon/cosima-utilities/blob/master/src/GazeboContactSensor.hpp