Feature request: Make select editable

[yopa]

Make the widget work like a 'suggest box' instead of a 'selection box'. Make this feature configurable (default is not editable).

This feature would not restrict options to the ones listed in the select (allows the addition of a free entry). This new entry would be added to the select options.

[pfiller]

Thanks for the feedback @yopa. This is a duplicate of #5, though.