profile: convert the "ruler item" to qt-quick

Code is mostly based on the "tooltip item". The dragging code was
slightly reworked to be more logical. A "disk item" was added for
the handles.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

profile-widget/zvalues.h

@@ -13,6 +13,7 @@ struct ProfileZValue {
 	enum ZValues {
 		Profile = 0,
 		Pictures,
+		RulerItem,
 		ToolTipItem,
 		Count
 	};