Support RxDeep and add an RxJS based List component based on it

[loreanvictor]

Why should it be added?

RxDeep provides most of the functionality of CONNECTIVE's deep states but offers following advantages:

• It is faster and more light-weight (no deep comparisons, MUCH fewer objects)
• It is strongly typed, which means it provides much better DX

What should be added?

A List component (i.e. RxList) which works with Observables instead of Pins and uses KeyedStates of RxDeep instead.
Perhaps it should even be switched to the default since CONNECTIVE is really for much advanced use cases.