Use Bootstrap button styles for filter submit
Use Bootstrap button styles for filter submit

* Make the action more prominent and consistent with the rest of the
application, also separates it a bit from the reset link below

alphagov/whitehall,robinwhittleton/whitehall,alphagov/whitehall,ggoral/whitehall,askl56/whitehall,YOTOV-LIMITED/whitehall,hotvulcan/whitehall,hotvulcan/whitehall,ggoral/whitehall,robinwhittleton/whitehall,robinwhittleton/whitehall,hotvulcan/whitehall,ggoral/whitehall,hotvulcan/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,YOTOV-LIMITED/whitehall,alphagov/whitehall,askl56/whitehall,robinwhittleton/whitehall,askl56/whitehall,askl56/whitehall,YOTOV-LIMITED/whitehall,alphagov/whitehall