Add database rollback API endpoint
Rollbacks API endpoint exposes multiple rollback jobs

Switched from single resource to multiple resource route and actions
Rename Rollback#rollback_to to Rollback#date for clarity

Causes unnecessary issues in tariff admin app
Make sure Rollback#date is a valid date

Refactor Rollback create response so it returns 201 (Created) and
presentation of Rollback job
Add sidekiq.yml config file
Synchronizer Rollback accepts date argument as Date and String

String has to be parsed to Date in order for Sequel to properly forge a
deletion query. Otherwise we loose data due to incorrect query.
Add Procile for Sidekiq startup

Just as Whitehall does have.
Remove Tire, Add custom search client

Client is based on official elasticsearch gem
Bulk serialize indexed models

Extracts serialization from Sequel::Model descendant classes to separate
serializer classes.

Removed Sequel pagination compatibility extension because it will not be
required any more since we don't use Tire.
Support for Elasticsearch in specs
Extract Serializer and specs to app/serializers

Separate concerns from persistance (Sequel::Model)

Also added index and delete methods to SearchClient. Refactored
interactors to use proper interface.
Remove references to Tire and comments
Remove Tariff indexer

Refactor reindexing code
Make searching work with new Elasticsearch client