Create GwtTestCase on the branch "typeahead-free-text"

[gabor-farkas]

The expected behaviour:
If the Typeahead allows custom test, it's always bound as String, with bindCustomText. This however doesn't affect the selectable options of the typeahead, they can still be of any type. So if the user selects a suggested value, if will be written to the presenter with the propert type. If the user enters a custom text, it will be bound to another presenter property with String type.

Things to test (allowing custom text):

• if a suggested value is selected, it's reflected in the target bound with typeahead.bind() (from abstractselect), and the custom text (the target of bindCustomText) is null.
• if a custom text is entered, the value will be null on the presenter (the selectedindex is -1 in the model), and the custom text has the user entered value.