Include multiple dictionaries in audit_conform

[brindakv]

The audit_conform category allows for one dictionary. This seems insufficient for I/H models, since the IHM-dictionary is an extension of the PDBx/mmCIF dictionary and the details of both may be required. For FRET-based models, the details of the FLR-dictionary may be additionally required. How do we include the details of multiple extension dictionaries that the data files are compliant with?