[ISSUE-22] Provenance and Agents

Hi All,
Please find attached updates to the provenance related data categories 
ready to be included in the draft. Many thanks to Phil for reviewing 
these in detail.

There are three separate data categories:
- Translation Agent Provenance: which record machines, people and 
organsiations responsible for translating the selected text

- Translation Agent Provenance: which records machines, people and 
organsiations responsible for revising the translation the selected text 
(e.g. from posteding or linguistic review)

- Standoff Provenance: which provides a link to standoff provenance 
record using the W3C PROV standard.

Comments welcome.

Regards,
Dave



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