Builder for cwl objects

[jefferys]

Might be nice to have a cwl object builder, which would work something like:

echoCwl <- newCwlObj( "echo" )
echoCwl <- cwlAddArgument( "message", "string" )
echoCwl <- cwlAddOption( "-e", "boolean" )

Position is managed by order added, with options before arguments. Can also specify if needed?