Create special COORDS set where frames remain on disk

loadtraj name <setname> [<filename>]

This command functions in two ways. If <filename> is not provided, all currently loaded input trajectories (from trajin commands) are added to TRAJ data set named <setname>. Note that if the input trajectory list is cleared (via ’clear trajin’) this will invalidate the TRAJ data set. In addition, currently all trajectories must have the same number of atoms. Otherwise add trajectory <filename> to TRAJ data set <setname>. TRAJ data sets cannot be modified.