Add option to show all Typeahead items

Created by: reefdog

Currently, the menu of items doesn't appear until you start typing. Normally this is fine, but sometimes I'd like the user to see the sorts of items in the list before typing.

I propose adding an option which, if set to true, goes ahead and shows the menu (along with first items number of items) as soon as the Typeahead input is focused. This option would default false to match current behavior.

So in the State example, when the input was focused, the menu would open and show Alabama through Delaware (assuming items was left at default 8). This prompts the user for the sort of string we're expecting them to type.

One could argue "but if we pop open a list of items, they may think that's all the items that are offered" which could be negated by #2042 (closed).