Enable ontology support for directories in addition to File and File[]

Hello,

We work in the image processing domain and we would like to be able to guarantee that a user has the correct ontology before submitting a workflow.

I posted this on the [discourse forum](https://cwl.discourse.group/t/potential-defect-in-ontology-format-checking/529) and it turns out that ontology is only working for File and File[]. We have a separate issue to log a warning if someone is using format field with a Directory class.

I'd like to request the ability to use ontologies for directory.