Merge pull request #6336 from RosettaCommons/roccomoretti/fix_slrl_patched
Fix issue with PDB_ROTAMERS for NCAAS.
Using PDB_ROTAMERS conformer files with NCAAs has an issue when you have patched residues (e.g. terminal).
Because the C-terminus patch adds an additional heavy atom, that causes the SingleLigandRotamerLibrary to hard exit.
Update the code to be more forgiving about missing atoms in the rotamers file, though attempt to maintain a hard error if we're missing conformer-defining atoms. (This will hopefully catch issues where the entire conformer file is malformed.)