Bug 1110966 - EOY fundraising home page takeover

Still somewhat in progress and I haven't added the waffle switch yet, but I wanted to kick off review. I think my JS for changing the form action is probably fairly hacky; I'd be very open to suggestions for a better approach.
Yeah, I kinda wrung my hands over it. I could recompile the custom font to add the one new character, and cachebust the new font file... Then once the campaign ends we'll just have the one extra icon, no need to update the font again to remove it. 80k is a lot, and this is the home page after all, it should be as fast as we can make it, and it's already a really heavy page... Maybe it's worth the effort.

Then again, we now seem to use Font Awesome so much around the site I almost wonder if we should just declare it in sandstone anyway. But then it adds weight to every page whether you need it or not... but then it would be cached... The hand-wringing continues.

I'll do whatever you tell me to do :)