Description

closes #84

Basically, I have rewritten _validate_table to use the frictionless Package object, instead of the Resource object.

This allows us to then pass in multiple resources and do the following:

• if "foreignKeys" is in the schema we collect together `schema["foreignKeys"][i]["reference"]["resource"]
• we go through and check if the referenced resource is a url (path), json object (data) or (the fall back) is a resource name that can be found within this ckan dataset; if none are true then we return a ValidationError
• these can be added to our Package object for frictionless framework to utilise during validation

Testing

TODO - I am working on these.

Documentation

I have updated the documentation to explain how to use foreign keys. It's fairly brief at the moment but probably in line with other similar parts.