Sample crystal structures with Crystalite for GenBench

Sample raw, unrelaxed structures and return the CIFs inline. 'unconditional' runs de novo generation with MP-20's atom counts; 'formula' runs CSP, cycling through the formula units that fit in 20 atoms (52 for larger formula units); 'chemical_system' runs CSP on one formula per sample, drawn from the system's stoichiometries.