[CWL] implement nargs=N

[mr-c]

From https://github.com/erasche/argparse2tool/blob/master/README.rst#limitations

nargs=N. Number of arguments can not be specified in CWL (yet).

This can be implemented using a http://www.commonwl.org/v1.0/CommandLineTool.html#CommandInputRecordSchema

Have N entries named 1..N, set the inputBinding at the record level.