Add oplog plugin for Taric models.
Identify records source and operations.
Oplogs and validations

Add Sequel oplog plugin for Taric models. Oplog dynamically defines
ModelName::Operation class to interact with Model's Oplog table. All
operations on Model are now append-only to oplog table.
Also introduces TradeTariffBackend::Validation. Since all ops are
append-only to oplog normal validations on model do not really work and
are not meant for that. Especially validation on callbacks like
before_destroy as there will be no destroying! Introduced our own
validation framework that as a bonus separates validation concern out of
Model class to Model::Validator class.