Remove `addModels` config from Read operation. Not relevant for proxies.
Add `isComplete` method to data.persistence.operation.Batch object.
Implement `loadRange` and `loadPageRange` for Collection.

Change all "load" methods to call callbacks and resolve/reject their Deferreds with a Batch object instead of a single Operation object, to cover the cases where multiple Operation objects are needed to fulfill a request. The 'load' event also now fires with a Batch object as well.