Centroid functionality
Centroid functionality

Added centroid functionality in order to optimise the contacts
clustering: now it will only compute rmsd if centroid distance
is less than target rmsd difference (since it is lower bound)

AdaptivePELE/AdaptivePELE,AdaptivePELE/AdaptivePELE,AdaptivePELE/AdaptivePELE,AdaptivePELE/AdaptivePELE