Extract RNA base pair info and metadata from loaded structures

Jalview could peek inside imported mmCIF files to look for additional metadata added by tools like FR3D and DNATCO.

As a starting point, we can look for additional data directly using the Jmol cif parser's internal datamodel:

cifinfo = getProperty("cifInfo")
print cifinfo
print cifinfo.keys
print cifinfo.models[1].keys
print cifinfo.models[1]._ndb_base_pair_annotation_id
print cifinfo.models[1]._ndb_struct_conf_na_feature