Added UpdaterCallback to Typeahead

The Typeahead plugin in gwt-bootstrap seems to be missing the update callback feature, so I added one:

When an item is selected in Typeahead, the registered UpdateCallback's onSelection methode is called with the item's suggestion as its parameter. The string that onSelection returns is put to the input field.

Also,  the JS typeahead no longer does any highlighting, so it's possible to use the SuggestOracle.Suggestion's display  string for displaying the results.