Define custom outputs outlet

[bear-in-a-box]

A single store emits data through one main output observable. Data can be manipulated (sorted, filtered etc.), though. It needs some standarized way to define custom outputs, even parametrized, so that one can subscribe to an output that fits their needs best.

[bear-in-a-box]

Initial work starts here. This includes helper methods for stores and standarized atomic output factory methods for loadables.