* First try at using DistViolationContribs
only the most basic of testing has been done
also add ForceField::distance2 to allow some optimizations
* allow testing using old approach
* optimization
At this point testUFFForceFieldHelpers fails since the check for std::max_element
in the e_contribs vector at Embedder.cpp:513 is now doing something totally different
(instead of a bunch of small distance violation contribs, we have one big one).
We'll need to come up with something for this.
With the benchmarking set that I'm using - 500 DG conformers for ~465 COD molecules
using 10 threads - this runs in almost 10% less time than master.
* backup;
builds, tests do not pass
* all tests pass except the old failure
* more constification
* backup/debugging
* add fourthdim contribs the same way
* tests now pass
* deprecations
* remove unused vars and code
* changes in response to review
