Allow to disable/enable from the BreakpointWidget

Added a context menu, for when a breakpoint is right-clicked
Removed the `itemClicked` behavior, since it would clash with the context menu

Source/Core/DolphinQt/Debugger/BreakpointWidget.h

@@ -46,6 +46,7 @@ private:
   void OnNewBreakpoint();
   void OnLoad();
   void OnSave();
+  void OnContextMenu();
 
   void UpdateIcons();