Rework the loops in symmetric precomputed rotamer-rotamer energy calculation to handle unusual setups.
This change improves handling of strange symmetries where the independent monomer is not first in sequence.
It also looks to reduce the memory footprint a bit, and may speed up packing, since it short-circuits
rotamer-rotamer calculations if the score_multiply factor for that residue pair is 0. It does not apply to
use of the linmem interaction graph, only the (default) precomputed energies interaction graph.
Two unit tests (zinc homodimer and beta strand homodimer) show logfile changes since the interaction graph
is now smaller.