The new user function arguments required for properly creating the pseudo-Brownian dynamics
simulation would have made the frame_order.pdb_model user function too complicated. Therefore this
part has been spun out into the new frame_order.simulate user function. The frame_order.simulate
frontend fully describes the algorithm that will be used to simulate the dynamic content of the PCS
and RDC data, and warns that not all modes of motion are visible and present.
