Change children slot to ignore criterias

[Charlie-Lucas]

Currently when you make 2 quantum you have 2 widget <=> children slot different, so the content disappear between 2 quantum of a widget tab. and you have to recreate all the content of the second quantum. We can move the children slot from widget to widgetMap and escape this but maybe the user want a new content. So the user must be able to choose between widgetChildrenSlot or the widgetMapChildrenSlot.