Updating the footer for edx.org and open edx.

Move the open edx logo inside the div

Adding a bunch of placeholder views.

indenting.

Making some styles work against LMS sass.

Adding back the old edx footer and associated icons, with a feature flag.
Merge pull request #4855 from edx/sanchez/update-platform-footer

Updating the footer for edx.org and open edx.