Create ISCAN corpus objects in scripts for compatibility

[mmcauliffe]

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).