Migrate in extra fields + replicate required data
use new methods to pull active/live revisions in
Enable saving to update new current/live fields + rename get_live to find_live in order to avoid conflict with getter/setters
Allow moving through revisions using new system
Don't forget the other revision-ables :o
Correct "create" action on save.
Fix tests
Update linkage on unpublish
Merge pull request #394 from unikent/feature/better-programme-revision-linkage

Simplify method revisionable items are linked to their current & live revisions.