Create ISCAN corpus objects in scripts for compatibility

At the moment only an ISCAN Database model is created via script, not the actual Corpus model.  This means that users cannot inspect/query a corpus that has been imported via script.  This should be a relatively straightforward fix (just adding a call in the https://github.com/MontrealCorpusTools/ISCAN/blob/master/iscan/api.py#L350 endpoint, maybe requiring some fixes).