Issue #381 clickable autocomplete

Made autocomplete to work with mouse.
I know the issue was created just a few hours ago. And was not yet approved by p-e-w. But I decided to implement it anyway. 
I can't find any reference to double click event in Clutter. Is there one?
If there is not, it should be implemented for the whole of finalterm not just autocomplete, because it will be needed in other cases (text selection by words, for example).