Use select to chose wikis

Use a select list rather than freeform text to enter active wiki data.
This should help the Committee by making the data uniform rather
freeform. This change also includes adding the Chosen jQuery plugin from
http://harvesthq.github.io/chosen/ to provide a nicer selection
experience for users with modern browsers.

Bug: 58226
Change-Id: Ie687da8c52eb7113f63b485375997997d9f0acdd