Proposal #5: Geocoder based on WFS spatial selectors

* New widget to perform WFS querys in cascade using geocoding spatial selectors.
* Append `ignoreExtraDims` on wfs search combo
* Make WFS search combo output format configurable.
* Add option on the Geocoder spatial selector to select different output format for the WFS search combo.
* Add `es` and `en` translations for this Geocoder.
* Minor fixes on feature summaries on spatial selectors

You can see [proposal page](https://github.com/geosolutions-it/MapStore/wiki/Proposal-%235:-Geocoder-based-on-WFS-spatial-selectors)