Editing can start by clicking into the widget or by pressing the toggle
button on the toolbar. In the first case the widget should emit a signal,
so the the toggle button's state can be up to date.

In both toggle button <-> LOK widget direction only update the state if
it's not yet up to date to avoid infinite loops.

Change-Id: I84c9e7757cd7cde42a95f67f0cb28f9ad6984e7a