Sensible ontodoc default options

[jesper-friis]

If the user doesn't provide the --pandoc-option-file option to ontodoc and there are on pandoc-options.yaml file in the current directory (for backward compatibility), then generate sensible pandoc-options.yaml and emmodoc-meta.yaml files with values inferred from options (like --format) and dcterms metadata in the ontology.

This will make ontodoc much easier to use.