[3.2][ticket/12649] Change sort & display options in footers to dropdown menu

https://tracker.phpbb.com/browse/PHPBB3-12649

![display-options](https://cloud.githubusercontent.com/assets/3015760/3282015/af48f930-f4d1-11e3-8ab2-0e644562cf6d.png)

Somewhat depends on https://github.com/phpbb/phpbb/pull/2504 for icons.
Ah I see. Which way do we want to go with this then?

![display-options](https://cloud.githubusercontent.com/assets/3015760/3395320/cb4ebf98-fcfb-11e3-8cc6-57590ec88538.png)

(in option 3 I removed the [go] button in favor of a checkbox onChange event)