Pop-up menu widget for selecting several items

In some circumstances it is more convenient to use a pop-up menu widget that is not closed when selection of the widget's sub-items is modified.

For example, the following menus must use this kind of widget:

1. "Translation frames" menu from UGENE-4737.
2. "Show/hide trace" in the chromatogram view.
3. "Graphs" menu.

Create a new widget and use it for the translation frames menu (separate tasks will be created for other cases).

The corresponding view must immediately be modified when selection in the pop-up menus is modified, but the menu must be closed only when the view is clicked somewhere else or when the icon, that opened the menu, is clicked again.