Compare trajectories to reference data

Compare trajectories to reference data

This introduces functionality to compare trajectories (x/v/f/box)
to reference data. It also allows to define the maximum number of
frames which should be checked. The latter allows to have a single
reference data, but decide based on the simulation setup (e.g.
parallelization scheme) how many frames are expected to match
before numerical divergence gets too large. To allow this, the
reference data functionality needs to give the option to ignore
unused reference frames.