Enhance CoSWID compliance

I added some things to make python-uswid more CoSWID compliant, which in turn makes it compatible with goswid.

tag-ids are now represented as a 16 byte UUID in CBOR/CoSWID (if possible) and as a hex string representation for all other formats
added the lang attribute to CBOR/CoSWID export
added numeric representation of version-scheme for export in CBOR/CoSWID
conform to 'one-or-more' CDDL rule in CoSWID

hughsie / python-uswid