Code enhancement - types for map layers

[ramtob]

Current state
Currently the map layers variables in Ansyn code are declared with type "any".
But we rely on the map layer object having methods like set() and get().
This remained from the time where we relied on using only OpenLayers map layers, because these objects do have these methods (set, get, etc.)
But we have since moved OpenLayers specific code to a separate package.

Target State
We will define a type for the map layers variables.