Joker-broker

* add rb.store intended for persisted redis interface

* objective.Toolbox from a ResourceBroker instance
* DeclBase.load_many from cache pipeline and single sql execution

* redis set and get many items using pipeline

* follow [this rule][1] and keep session away from Model
* unify NoncachedBase and CachedBase into DeclBase

* `as_json_serializable` support fields selection
* `joker.cast.represent` for `NoncachedBase.__repr__`
* add `NoncachedBase.load_many()`


0.1.2cc
* apply `abc.abstractmethod` for `cls.get_resource_broker()`

* `rb.standby` randomly pickup from `rb.standby_interfaces`