[#56] Check if the API actually returned something
Use actual dataset id when sending file API calls
Add missing auth function
[#56] Update file creation handling

From iteration 4 all audits related to File creation have a VersionId
regardless of whether they are new files or new file versions. We need
to always call the file_vesion_show endpoint and decide if we need to
create or updated by checking if the resource exists or not.

Note that the necessary endpoint is down now on the platform so this can
not be live tested.
Update schema for file URLs

As of latest iteration Platform File URLs are stored in the
`FileExternalUrl` field on the metadata. Apart from that if the file is
hosted externally, there is an `ExternalUrl` field with the external
url.
Merge branch 'master' of github.com:okfn/ckanext-glasgow