Update default CS and Projection for layer

[AliyanH]

• update default cs from pcrs to gcrs, closes Change the default coordinates for a layer from pcrs to gcrs #852
• add a default projection (parent's projection) for a layer (when projection map-meta is not provided), closes Layer does not render without map-meta name="projection" #851
  • console logs, when map-meta not present for a layer.
• Add default projection of "OSMTILE" to a <mapml-viewer> with no projection attribute #860 handled in Add a default projection (OSMTILE) for the map #873
  • Add web-map equivalent
• Add Testing

[prushforth]

Looks good to me, tested with geoserver too. I noticed that in mapml2geojson.html / test there are some comments like this:

<!-- Setting the geometry coordinates to gcrs, as the default is pcrs -->
            <map-geometry cs="gcrs">

so maybe we should amend that test / others that we may find that set the default CS and projection via map-meta or cs attribute to RELY on the new default values for these? At least we could remove the comment because it's no longer true that the default is PCRS.

[AliyanH]

Is this ready to merge?

I believe so, do you think the testing is sufficient or can you think of any other edge cases? I will give it a second look also.

[AliyanH]

@prushforth in ca9399d, default projection was added, and the use of 'createmap' events was removed.

Though there is still a bug with the _processInitialExtent/_initTemplateVars, this occurs when the map is initially loading and the custom projection is not available, so the layer's extent gets calculated (_processInitialExtent/_initTemplateVars) based on the map's current projection (OSMTILE) - which throws errors (can be seen in the BNG experiment).

I think the layer/extent needs to go disabled at that stage and not go through that code at that time, and the layer should only be loaded once the current projection is available with the use of 'projectionchange' events emitted by mapml-viewer, which the layer will be listening for.

This will be handled in #873.