Issue43
This enhances the zooming functionality of the GUI Diagram (in the mainframe and spawned windows). By holding down the left mouse button the user can draw a transparent blue rectangle to mark the area they want to zoom in. The zoom will be carried out when the left mouse button is released. This zoom function can be applied several times. By clicking the right mouse button the original axes ranges will be restored
Resolves #43 (closed)
Edited by Trageser