50000203 database rollback api endpoint

This change is for https://www.pivotaltracker.com/story/show/50000203

Adds API endpoint and infrastructure for rolling back database to specific date with ability to redownload updates.

Depends on:

* https://github.com/alphagov/trade-tariff-admin/pull/18

**Puppet/alphagov deployment needs updating for redis/sidekiq**