Added migration for new under_review field in programmes_revisions

Also made a minor comment edit in programmes controller
Add review button instead of two current buttons
Add review views + refactor diff logic to own function
Cleanup comments
Merge branch 'feature/under-review-workflow-317' of github.com:unikent/programmes-plant into feature/inbox-ui-changes
Merge branch 'develop' of github.com:unikent/programmes-plant into feature/inbox-ui-changes
Use undereview flag to populate inbox
Switch submit_revision_for_editing to use new toggling method. Move to make programme only feature
Update UI to show new approval system + remove any waiting revisions from que for that programme
Move tests
Correct message display for revision_header
Correct revision bar behaviors
Clear references to under_review state
fix typo
Clear lock message and previous awaiting approvals on save
Merge branch 'develop' of github.com:unikent/programmes-plant into feature/inbox-ui-changes
Fix tests
Fix notification title, being just ":title"
Fix locking message showing on other revisionable types
Stop invalid revision state breaking programme - instead show warning.
Fix revisions not been removed from approve queue correctly