[view.elements.components] add private accessors to Switch - children get self._switch() and self._knob() so that if the underlying   implementation of the element subtree changes, it remains opaque to   containers where these are in the parent div's children. Switch is   implemented as a Div with a couple children, and Switch containers shouldnt   need to know which child the checkbox and span are to modify them.
[view.elements.components] add private accessors to Switch
- children get self._switch() and self._knob() so that if the underlying
  implementation of the element subtree changes, it remains opaque to
  containers where these are in the parent div's children. Switch is
  implemented as a Div with a couple children, and Switch containers shouldnt
  need to know which child the checkbox and span are to modify them.

scrbrd/scoreboard,scrbrd/scoreboard