WIP Issue 107 revive and improve FeatureInfoWindow

[justb4]

As stated in #107 FeatureInfoWindow (FIW) was somewhat disconnected from Wegue for historic reasons. This PR is WIP to revive and hopefully enhance again:

Summary of changes:

• config: make configurable again
• config: prev version could handle one layer(Id), now multiple layers
• config: more config options: Info link ("More..."), text area (description), CSS-related
• FIW: template enhancements
• FIW: use ES2015 syntax like arrow function (no need for var me=this!)
• WguAppTemplate: import and create
• config: two OGC OpenAPI Features Layers (dutch castles and windmills) with Image and Info link attrs
• config: FIW with these two Layers
• styling: allow for icon style Point styling
• config: also enable FIW in app-conf-projected.json
• wildcard config spec: e.g. multiple Layers for FIW with similar attribute mappings
• how to configure selected Icons in Style and switch on Map
• use slots in FIW template
• more unit tests...

Let's first see if this is inline what is expected. We are actually going to deploy this in an app.