Fix Bug 1016500 - Implement Manifesto redesign

Do not merge yet. Still needs photo usage permissions and l10n.
Curious what the issue is with IE7 - aside from a few minor styling issues, the modal seems to work ok if I remove the UA sniffing?

It's not a concern really, but we should try to avoid UA sniffing in general unless it's really necessary (i.e. like providing the right download content, or if something can't be feature detected). I think it would probably be fine to serve really old browsers the no-JS version of this page using a conditional comment - thoughts?