Not use the maxzoom as test zoom in create layergroup
Remove unused, redundant and duplicated declaration variables
Clean createLayergroup
Remove layer check metric as it is no so important right now
Move getTileOrGrid to MapBackend
I failed to include mapBackend instantiation lines
Moves getFeatureAttributes into MapBackend
Moves fetchTilesetMetadata to map backend
New backend to attempt to retrieve from map backend
Adds tryFetchTileOrGrid to it.
Moves tryFetchFeatureAttributes to map validator backend
Some notes about what a backend should and should not be.
Merge branch 'split-create-layergroup' into static-controller

Conflicts:
	lib/windshaft/server.js