Summary & Grid > Don't display widgetPanels when they are empty

We should be able to style (add borders, update margins, ...) the widget boxes in the grid.

Today it's not possible since there is no other solution than put the styles on widgetPanels, but the empty widgets slots make this action not possible. See screenshot.

We should see if we can move the widgetPanel in another level, add a new step in the grid (.gridContainer -> .gridRow -> .gridColumn + .gridStyle** and then -> .gridBox).