Pointer cleanup (#242)

- Made greater use of smart pointers, eliminating many instances of manual memory management
- Do not use pointers at all for many non-polymorphic classes
- Assorted other code cleanup

glabels/VariablesView.h

@@ -47,7 +47,7 @@ namespace glabels
 		/////////////////////////////////
 	public:
 		VariablesView( QWidget *parent = nullptr );
-		~VariablesView() override;
+		virtual ~VariablesView() = default;
 
 
 		/////////////////////////////////