* feat: inform child widget to do some custom cleanup
* fix: type
* refactor: restore old removeChildDomNodes
* refactor: make destroy() a separate method
* refactor: make destroy call removeChildDomNodes
* refactor: call destroy instead of removeChildDomNodes in each core widgets
* fix: refreshSelf does not mean destroy
* refactor: use old var insteadof const
* docs: about subclass