Validate generated CWL TypeScript models with CWL conformance tests

[ZimmerA]

Before merging #2 the schema models have to be validated against the conformance tests found in https://github.com/common-workflow-language/cwl-v1.2/tree/1.2.1_proposed/tests.

For this @mr-c suggested the following approach:

1. Load all tests that are not marked with should_fail: true
2. Save all documents using their save() function and validate the output with cwltool --validate
3. Run the tests with the newly saved documents in place of the original documents