NCS and R/R free

From CCP4 wiki

[http://dx.doi.org/10.1107/S0907444905040680 Fabiola, F., A. Korostelev, et al. (2006). "Bias in cross-validated free R factors: mitigation of the effects of non-crystallographic symmetry." Acta Crystallogr D Biol Crystallogr 62(Pt 3): 227-38.]