With this commit the progress report in the
`dtc` subcommand `export` determines the number
of records to process and displays a
known-size report, i.e., a percentage based
progress report.
With this commit export will by default remove
the `schema-type` attributes from stored records.
The option `--keep-schema-types` instructs `export`
to keep the `shcmea_type`-attributes in the
stored records.
