SUF.mapLayers is now awkward

[davesmith00000]

mapLayers was introduce to SceneUpdateFragment so that you can ...map over the layers... and modify common attributes.

With the recent changes, you are now mapping over LayerEntrys and the Layer ADT, which is far less convenient.

This is probably a more subtle problem than it seems, for instance if you make a mapContentLayers method, should it map over top level content layers or nested ones too?