Tidy up and simplification of UI

Removal of sliders and zoom / rotate buttons.
Rearrangement of buttons to reduce amount of grey space.
Reduction of size of preview and of main window.
Smaller, tigter layout works better on small screens and is less complex.

frontend_qt4/mainwindow.h

@@ -116,11 +116,6 @@ public slots:
 	void datamatrix_options();
 	void maxi_primary();
 	void change_print_scale();
-	void scaleRotate();
-	void zoomIn(void);
-	void zoomOut(void);
-	void rotateLeft(void);
-	void rotateRight(void);
 
 private slots:
 	bool save();