for all 'single-outputfile-exporters':
if the given outputFile is a directory: export into a new file in that directory
otherwise: use the given outputFile as is, and create all parent directories (if not there already)
also: make each exporter define it's default file extension
... so that we can use exporters generically from the outside, while using
their specific correct file extensions for the resulting files
for all 'single-outputfile-exporters': if the given outputFile is a directory: export into a new file in that directory otherwise: use the given outputFile as is, and create all parent directories (if not there already)
also: make each exporter define it's default file extension ... so that we can use exporters generically from the outside, while using their specific correct file extensions for the resulting files