Revert operations from a particular timestamp

We want to be able to rollback some changes that were made since a particular timestamp.

Since clients expect that timestamp never go back in the past, the idea would be to apply the reverse operations.

It would take the history entries from that particular timestamp and apply the opposite operations (deleted records get recreated, etc.).

The permissions would be restored too.

It would fail if the history is not enabled or if the oldest timestamp of the history is superior that the one specified...

Thoughts ?

It could be:
- A command `$ kinto revert --auth user:pass --bucket=test --collection=images 123456789`
- An endpoint provided by the history plugin `/buckets/tests/revert?_since=1245`

(_It could be a feature exposed in the kinto-admin too_)