Add form-control class to select2 element

* The select2 overrides are more specific and only apply fixes to
elements with a form-control class. Normally this is passed through to
the select2 widget but the business support script is generating a
hidden input
* Add form-control to the hidden input when it’s created
Fix alignment of checkboxes on business support

* Checkboxes were using a markup pattern from Bootstrap 2 that appears
to have broken with a Boostrap 3.2 upgrade
* Use the recommended pattern from
http://getbootstrap.com/css/#forms
Enhance user select drop down with select2

* Allow users to search the list of users instead of having to scroll
up and down