Minor correction to TreeModel.get_path to allow for subclasses that use an alternate...

Minor correction to TreeModel.get_path to allow for subclasses that use an alternate level attribute. Minor correction to TreeManager.get_with_path to only return root as the deepest node if there is actually no deepest_found node. Added MultiView.reverse() shortcut method to handle the common pattern of getting the absolute url for the subpath of a multiview. Adjusted waldo MultiViews to use their reverse() method. Added make_confirmation_link() method to LoginMultiView to provide a standard, reusable way to handle this task. Brought waldo's multiview get_context method use in line with penfield by removing the optional extra dictionary passed in.