ENH: Editor: Effects are checkable and updated based on the parameter node

This commit ensures the button effect are checked or unchecked based
on the 'effect' property stored in the parameter node.

It also extends the EditUtil API adding function allowing to more easily
set and get the 'EraseLabel' state.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23636 3bd1e089-480b-0410-8dfb-8563597acbee