PLAT780 Type_1 Test whether coordinates form a connected set

Atoms given in a CIF should form a 'connected set', i.e. no symmetry
operations are needed to get atoms in a bonding position. A connected set of
atoms is not needed for the least squares refinement (unless hydrogen atoms
are to be added at calculated positions). Geometry listings (bonds, angles,
torsions & H-bonds) become unwieldy for non-connected atom sets.