added convenience method
Mockup for Cargo-ANTs is starting to work. Trajectory messages are
being honored, the vehicle (just a rectangle with holonomic drive)
will do sequential pure rotations and translations to get to the last
point of a trajectory, just to see whether information flows and is
more or less consistent.

To test this:
- clone into catkin workspace
- catkin_make
- start roscore
- run nepumuk with the cargo-ants.yaml configuration, i.e.
    ./devel/lib/sfl2ros/nepumuk -c src/sfl2/ros/cargo-ants.yaml
- press 'c' in the simulator window
- send a trajectory message, i.e.
    rostopic pub -1 trajectory cargo_ants_msgs/Trajectory '{trajectory_id: 42, points: [{x: 20, y: 11, th: -1}]}'