Add WMTS and WMS layer components for 3D

[vladyslav-tk]

Test link

[pakb]

don't know if it would make sense to directly use the same logic as the one for OL, meaning :

:projection="layerConfig.isExternal ? WEBMERCATOR : LV95"

Some of our WMTS layers do not behave totally correctly when requested as EPSG:3857 or EPSG:4326

[vladyslav-tk]

Cesium makes wrong requests when using LV95 for WMTS layer

[vladyslav-tk]

maybe we can investigate and try to use WebMapServiceImageryProvider instead of UrlTemplateImageryProvider if LV95 required for WMTS

[pakb]

let's keep mercator there then, it's something we should investigate if we want to have LV95 projection for 3D in the future (I doubt it's a good idea anyway, for 3D at least)

[vladyslav-tk]

You do not state that you require a createImagery(...) method, and its input/outputs
You are watching url in the mixin, but it is never stated that this is required by the mixin

I added this to the doc

I don't know if this would align nicely with future GeoJSON and KML implementation, maybe you could require that the component using the mixin provides a Cesium.ImageryProvider() as this.provider and you could react to changes to this provider directly. Don't know if it would be better in regards to future GeoJSON and KML implementation?!

We can't use this mixin for GeoJSON and KML because it will be not imagery layers and zIndex, opacity, and URL will be handled differently. Maybe I will create one more mixin, more general

[pakb]

looking good! small issue with opacity to fix, and some unnecessary WMTS check in the utils function and we should be good to go!