Currently, there is a circular dependency between the `oplog` library and `catalog_impl`, which links just because the Collection class is virtual. With CRUD (or rather any writing code) being pulled out of CollectionImpl, this class will become the lowest possible denominator for operations against the catalog and it will be below the `oplog` hierarchically.

Temporarily they will have to interact through the `LocalOpLog` interface and this ticket is to perform this decoupling.