Fix selects in ie

Story: https://www.pivotaltracker.com/story/show/73412800

Previously, select boxes on the frontend filters were displaying with two down arrows - one from the background image, and one browser-rendered dropdown arrow. This PR strips out the more complicated select styling for IE version <= 9.

I needed to introduce an IE9 stylesheet to achieve this.

This PR also rationalises the styling between the publications filter and the stats announcement filter.