new req for dumping CommandLineTools inputs into a "cwl.input.json" file

[mr-c]

• does the cwl.input.json file go in the working directory?
• If so, how does this interact with InitialWorkDirRequirement?

Possible example:

Before:

requirements:
  InlineJavascriptRequirement: {}
  InitialWorkDirRequirement:
    listing:
      - entryname: cwl_inputs.json
        entry: $(JSON.stringify(inputs))
arguments:
  - -ini
  - cwl_inputs.json

After:

requirements:
  InputsAsJson: {}  # default name is "cwl.input.json"
arguments:
  - -ini
  - cwl.input.json

or very concisely, perhaps:

arguments:
  - -ini
  - ${InputAsJson}  # resolves to a random filename ending in ".json" located not in the current working directory