toggle => update_visibility for clarity and module name

* The usage of toggle in the visibility code and the inverse logic
  (that hide had to set hidden to false, then call toggle because
  would inverse it and then notify the GUI) was bugging me for
  some time. It worked well, but it was tricky to understand and
  reason about. Furthermore, the backend code that was named
  "toggle" only set the visibility based on the DSL. Nothing was
  toggling there so the module and method_name were inappropriate
  to start with :-) I think this makes it much easier to read :-)
* sorry for the many changes - renames and stuff. But RubyMine did
  ans awesome job supporting me!