Make default selected vector layer configurable

[timroes]

When creating a new region map we by default select the first vector layer returned from the tilemap server. Since those are alphabetically sorted (what most likely make sense), we currently always select Canadian Provinces as the default vector layer. I think it would make the most sense for a broader user group to have "World Countries" selected as the default.

There could be several possible implementations to that:

• Create an advanced setting, what layer should be the default layer. Pro: easiest editable; Con: you would need to match layers by names
• Extend the manifest format returned by the tilemap server, to contain some information what the default vector layer is. Pro: clear format, could be more easily configured for all Kibana instances if we e.g. would rename layers; Con: Logic might be more complex, if you have custom vector layers? which default settings would have priority?

[thomasneirynck]

imho, the manifest should enforce the "default" ordering. This would be a tidy way to provide a good initial experience. I agree that countries should go on top, followed by alphabetical sort of other "sub-divisions".

[thomasneirynck]

Layer ordering is now determined by EMS, and is configurable. It is now alphabetical, with world-countries on top. thanks @mentat!