add new processors which compute the fundamental diagram and add a VTrajectory class which supports some helper method to analyse a trajectory.

This is needed because the SourceController spawns pedestrian based on
on the rectangular bound. Thus the pedestrian cannot be placed
*completely* within a circle with radius 0.4 although there would be
enough space.

add processor which writes out each small step (PedestrianFootStepProcessor). If the information is available the PostVis will use it.