Merge pull request #3789 from RosettaCommons/JackMaguire/HBNetFlatSet
Replacing HBNet's sorted vectors with boost flat_sets
One of the messiest things I added to HBNet was sorted vectors. They helped with performance but littered the code with `std::lower_bound` and `std::binary_search`. I'm going through and replacing them with boost's flat containers (ordered sets and maps that are built on top of vectors) to keep the performance benefits without all the mess.
Thanks to Brian for the review!