Make `select` elements in search form of Test Exchange searchable by text

[georgemsun]

Dropdowns are getting long and it would be easier to type in a phrase to pull up an entry than scan for it alphabetically.

[georgemsun]

1. https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/css/select2.css
2. https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.min.js