Improve logging for PinchMap
Remove old layer restore function

It has been used before the persistent overlay group support has been added
and has been still run by mistake, effectively fighting a race condition
with overlay group loading and potentially overwriting the base layer with
a bogus value.
Fix a race condition preventing some tiles from working correctly

There was a race that could prevent them from working correctly by breaking their
initialization by clearing the layers data model when restoring saved layers.
By instead replacing the initial item we can prevent the race and everything
seems to work fine. :) Still, if it turns out that loadLayers() needs to be called
after initialization in the future, this would need to be extended to handle an
arbitrary number of existing layers when loading saved layers.