panelWidget: Do not override show() method

Created by: matthijskooijman

This widget defined a show() method, which would show the menu. However, show() is already a method defined by some class higher up in the hierarchy, which makes the widget in the status area visible. By defining a show() method here, the behavior of the show() method changes, causing issues.

One such issue showed when combining this extension with the status-area-horizontal-spacing extension, which calls hide() and show() on each widget in the status area. With the overridden show() method in the hamster extension, this would hide the widget and then show the menu, breaking the extension because the widget would stay hidden.

This commit renames show() to show_menu() to prevent to conflict. It seems that the method was not actually used, so no references were updated. For consistency, toggle() is also renamed to toggle_menu(), with one reference updated.