Add SciX ID to output

[ehenneken]

Currently the service provides output like

{u'resolved': [{u'refstring': u'Drake, J. J., 2021. ApJL, 922, L42. doi:10.3847/2041-8213/ac34fd', u'score': u'1.0', u'bibcode': u'2021ApJ...922L..42D', u'id': u'H445I1', 'scix_id':'scix:2N0B-6359-55CE'}]}

With this change, the output will include the SciX ID in case of matches, like

{u'resolved': [{u'refstring': u'Drake, J. J., 2021. ApJL, 922, L42. doi:10.3847/2041-8213/ac34fd', u'score': u'1.0', u'bibcode': u'2021ApJ...922L..42D', u'id': u'H445I1', 'scix_id':'scix:2N0B-6359-55CE'}]}

The SciX ID is always available for matched records, as it is the canonical identifier for all public records and can be retrieved from the Solr response for the matched record.