Improve support for Context/S layered methods

[LinqLover]

This is cool but not really what I would have expected:

It would be nice if I had the possibility to edit layered methods just like it is possible by using the normal CodeHolder interface.

Still, it is very cool that this representation reveals the layered method. Maybe the tree structure could show each version of the method in a separate node?

In the ContextS Browser, I would have expected that selecting a single layer shows it in the Sandblocks representation, but the representation does not change depending on the layer, currently.