DataController migration documentation

**Affected Projects**
React

**Is your feature request related to a problem? Please describe.**
Was looking through the change log and the new documentation but could not find any reference to the deprecated DataController.

**Describe the solution you'd like**
Would be great to get some documentation on the recommended way to migrate from using DataController to not using it.

**Describe alternatives you've considered**
I tried using defaultQuery on the ReactiveList but it doesn't react to the other components and also doesn't respect the `size` prop on ReactiveList. I am going to attempt to use ReactiveComponent now instead to build my own DataController but would be good to get some clarification on best approach.

Just out of curiosity why was it removed?