This is an attempt to get rid of all the custom code we have everywhere that saves the state of dialogs and tool option widgets to kritarc. It simply iterates over the child widgets of widget and when it encounters one that it knows how to save the state for, it saves it. Restoring works similar, but it's possible to override restore values.

Todo:

• port all our tools
• check whether this breaks the math-enabled edit widgets
• add more widgets we can save the state of
• make sure that in every place where we use this widget, the widgets we want to save the state of have object names.

See also https://bugs.kde.org/show_bug.cgi?id=408601, for instance