Additional evolving of Orchestra.Examples.Ribbon.Microsoft

1.  OpenRecentlyUsedItem, UnpinItem, PinItem and OpenInExplorer commands are added to the example as well as initial implentation.

2. Bug for the case when items aren't updated in UI after changes is fixed.



Don't do event subscriptions in the ctor. Use it in the Initialize method and unsubscribe in Close so VM's will never cause memory leaks.