Users now have a choice:
* The new way: The field to enter words located like in all browsers, in the toolbar.
* The old way: to search in the sidebar.
Both UI modes are supported and can be switched between via View -> Search Pane menu.
It is a separate detacheable pane, which could also be enabled/disabled,
it tracks the current tab's contains, and lists those dictionaries that
contributed their content to the current translation.
Clicking on dictionary name jumps to the appropriate article from
this dictionary, which improves the navigation flow.
The Dictionaries Pane:
* Shows both dictionaries' names and icons.
* Does not consume resources when hidden.
* Properly styled.
* Properly handles app-wide shortcuts
(Esc, Ctrl-L, Alt-D, Enter, Alt-Up/Down).