ComponentBase: Consider setState(updater) instead of setState(object)

[ms-markda]

I don't have evidence that this is hurting us, but the React docs are quite clear that if building state depends on previous state then we should use the updater version instead of the object version. At the ReSub layer, we don't know if the derived class will need this should perhaps we should always opt-in to be safe?

Also, we could forbid using this.state for the previous state since the updater is given prevState (and props). Although that would involve changing the _buildState signature to forward it like the props.

One possible issue: how does the props argument correspond with nextProps in componentWillReceiveProps? Which should we use in there?

https://reactjs.org/docs/react-component.html#setstate