Convert filter links into standard form buttons

With this change, the filter box links shows as follows:

![screen shot 2014-11-23 at 12 59 41 pm](https://cloud.githubusercontent.com/assets/1354889/5159208/bd17d136-7310-11e4-89e1-46d542397029.png)

Fixes #17834
http://www.mantisbt.org/bugs/view.php?id=17917