Minimum window size

[lelaus]

Currently there is no minimum allowed size for the window that contains the GUI. This means that the widgets overlap when the window size is reduced. It would be better to allow resizing down to a minimum dimension value to avoid overlapping. The self-adapting behavior is currently only present in the inner components, not in the outer ones. Each time a resize action is required, all components of the GUI should remain visible until the minimum size is reached.