Start integration of mockup design
Start import of css, images, and html from mockup (https://github.com/mray/freedombox.org-mockup).
- Only started implementation of landing page, and only the parts with content that is already available. (In other words, there's no content other than the "welcome" text, and links at the bottom.)
- Skipped importing unused images for now. I cropped logos.png to only include FreedomBox and Debian logo, since we don't have permission to use the other organization's logos yet.