Merge pull request #3776 from RosettaCommons/roccomoretti/upper_atom_selector
Convert UPPER_POSITION patch selector to UPPER_ATOM selector.
The UPPER_POSITION patch selector currently has a dependency on the CarbohydrateInfo object. This makes the selector not as general as it could be. I've changed this to an UPPER_ATOM selector, which cues based on the atom name of the atom connected to the UPPER connection, rather than the mainchain position setting in the CarbohydrateInfo object.