New class called PanelController:
is a new QWidget shown when the user clicks on the panel toolbox, it's a thing that will eventually replace the panel configuration dialog.
at the moment it has an add aplet and remove panel buttons.

it is possible to resize the panel by dragging the upper edge of the panel controller and in the future will be provided a way to resize the panel width and changing the position.
at the moment there is the known problem that the resize handle doesn't work for vertical panel for now.