Allow downloading and restoring configuration from audit history
Currently the audit API can only return an HTML annotated view of the changes made to configuration elements like variable sets and deployment process. This is not helpful when the configuration is huge or when we need to find changes over multiple edits of the same configuration.
Proposal: add the ability to download the raw JSON that was in effect after the change. The result should be equivalent to what we would get by clicking 'Download as JSON' after making the changes.
This would allow us to:
- create diffs between arbitrary dates, not just a single entry in the audit log
- restore configuration to a previous state (using existing APIs).