#1 Support of nested menus

[Vasyl Pasternak]

I added support for nested menus for Option menu.

The nested menus defined like the following:

menu = [('item 1', handler1),
('item 2', handler2),
('item 3',
(('subitem 1', handler31),
('subitem 2', handler32))),
('item 4', handler4)]

[Vasyl Pasternak]

Patch that implements nested menus in Options menu