New map mode and module `addResourceMode`

* When user chooses resource type, fetch and install detail fields using type-specific template
* Only enable final "Next" button when all fields have been filled in
* Show/hide subquestions depending on yes/no answer

Also:
* `safe_get_model_class` now looks in `map_features` app as well as `treemap`
* `reverseGeocodeStreamAndUpdateAddressesOnForm` now works with e.g. `rainBarrelLA.address_*` as well as `plot.address_*`
* `formToDictionary` now handles radio buttons