Entity heading while following a trajectory

Created from #255 (closed)

Description of the problem
The definition of the orientation of an entity while following a trajectory is inconsistent for the different trajectory shapes (NURBS, Polyline, Clothoid). For Clothoids there is no possibility. For NURBS the orientation can be defined within the control points, but they don´t necessarily need to be on the trajectory.

Description of a solution
A consistent/common possibility (outside of the shape definition) should be the goal.
Furthermore only if the following mode is "position", then the orientation should be taken into consideration. Otherwise the orientation as well as the position of the entity is determined by the dynamic limitations of the entity and calculated by the controller.
A first suggestion can be found here

Additional information
The solution should be also consistent with the new definition of the timing of an entity while following a trajectory. See #141, #191 (closed) (Meaning of time attribute), #122 (closed) (clarification of all NURBS attributes).

#224 (closed) (example of NURBS/heading "non-user-friendly" definition) related wiki page.

#172 (closed) (order of control points/vertices) #173 (closed) (clarification of behaviour at the start of FollowTrajectory actions - related wiki page