Improve UX of Branch Selector

Currently, the branch selector will only show the top 50 branches, ordered alphabetically.

This is confusing users, since there is no indication that:

• the list is truncated
• they can set any of the missing branches by typing in the text area at the top.

At the very least, we need to:

• indicate the dropdown contains truncated results
• mention the other branches are available when typing.

Ideally, this widget would not be a dropdown. It would simply be a type ahead. That way, there could be less confusion.

14 Jan 2013: There is a temp server set up for DoT - http://172.22.3.56:6060/foo/browse/sanity1. Contact lzheng if there is any problem of the server.