Migrate custom fields that match common core metadata

There's at least one place where one of the fields in the common core metadata is shown as a separate custom field. On the record for [Best of Charts of Note 2013 ](https://inventory.data.gov/dataset/best-of-charts-of-note-2013) the `dataQuality` field should be handled by the "Meets Agency Data Quality" dropdown menu. The way it's currently handled as a custom field is causing it to be exported as a string rather than a boolean.

I'm not sure if this was an issue with a direct import that was converted incorrectly or if it's legacy from data entry before the option to specify "Meets Agency Data Quality" was implemented, but any custom field that matches at common core metadata field like this need to be mapped properly.

This was initially reported at https://github.com/GSA/project-open-data-dashboard/issues/31

Start by examining how the Best of Charts of Note 2013 record handles the dataQuality custom field and the "Meets Agency Data Quality" dropdown. Trace the common core metadata mapping and export behavior, then verify that matching custom fields use the dropdown representation and export as booleans rather than strings.

Written by the indexing model from the issue text.