Add status filter to user list
Whitespace: User index indentation
Add filtered user counts above users table
Move user filters into partial
Move user filter methods to separate helper
Use the same methods for role and status filters

Abstract out the filter type to make management of filters easier and
simplify markup.
Port filter styles from Transition app

Bring across white filter styles from Transition. These should
eventually live in the admin template.

* Introduce a nag-compact style which has less padding
* Highlight active filters
* Introduce a remove filter button
* Reduce size of chevron in filter
* Add ‘pill’ styles for text only items in a nav-pill container
Add a 'remove all filters' link

Quickly return to the original list of users