Added setElementLocked and setElementVisible methods to Layer class to work around bug with those dom methods where the elements are indexed differently than the elements array.
Use dom methods to set Layer properties like locked and visible, and return false for the root layer.
Attempted support for creating a LayerTree on a different frame, but needs to be backed out.
Added currentTopLayer property to LayerTree.
Switched back to using the current frame and not providing a way to create a LayerTree on a different frame.
Updated docs.