Merge pull request #2030 from RosettaCommons/rhiju/6D_loop_close
implicit treatment of RNA loops via precalculated 6D tensors
• tests were run (except icc build, which is stuck; was run in a previous test, though) -- integration test changes are all expected (the ones that fluctuate; and a few are effected by new score term `rna_stub_coord_hack`): http://benchmark.graylab.jhu.edu/revision?id=5686&branch=