Refactor the managers for datastores

There is a large amount of boiler-plate code in each datastore manager. As more managers are added, the time involved in maintaining all this code will continue to grow. To alleviate this, a base manager class needs to be created where all common code can reside.

Within the context of this refactor, the issue with having instances flip in-and-out of BUILD state can be addressed properly. In the absence of a base class, this would have to be implemented in each datastore, potentially leading to bugs in one datastore that don't exist in another.