Add untyped base view model for static view models

[marner2]

Waiting on #523

View changes without #523

Extracted a helper for the view models and used it in a new BaseViewModel and the existing internal DynamicViewModel. Since we have not yet merged in #512, we cannot infer the types nicely yet and much manually cast them on each view model.

~~Remaining work: add support for sub models bindings with BaseViewModel.~~ Done