Allow filtering of user list by user status

https://www.agileplannerapp.com/boards/173808/cards/9014

Create a filter so that users can be viewed by the following statuses:
* Suspended
* Invited
* Locked
* Passphrase expired
* Active

Changes:
* Replace suspended column in user list with a status column
* Ports filter styles from Transition app
* Tidies up role filter UI, makes it easier to remove filters
* Allows filtering by role, status, name/email at the same time
* Adds a count for users displayed

Suggest reviewing with `?w=1` because of 36528f0

## Filter by status
![screen shot 2014-12-23 at 14 43 33](https://cloud.githubusercontent.com/assets/319055/5538873/33ffddda-8ab2-11e4-8f4c-fdb64db5d7be.png)

## Filter by role and status
![screen shot 2014-12-23 at 14 43 57](https://cloud.githubusercontent.com/assets/319055/5538874/34033e76-8ab2-11e4-98de-64d284e94fc0.png)

## Statuses
![screen shot 2014-12-23 at 14 45 35](https://cloud.githubusercontent.com/assets/319055/5538893/67bd5d8c-8ab2-11e4-9e89-ade3da3e4661.png)