Additional Render Strategies

[elbakerino]

The core should already support multiple render strategies, it's just a matter of reusing base components.

For an example and as it provides some special flexibility for some use cases, currently thinking about survey schemas, an additional strategy renderer similiar to jsonforms.io would be great, example of category schemas.

Should reuse #104 for view into data schema merging.

[elbakerino]

With 0.3.0-alpha it is now possible to implement any render strategy, bind a custom WidgetRenderer to widgets.WidgetRenderer, maybe reuse the matcher function: widgetMatcher. Then with the own WidgetRenderer, someone can replace ObjectRenderer/VirtualWidgetRenderer with own implementations.

Reusing the core functions will be further optimized in 0.4.0 with #100.