Add Django apps for student account and profile

Add Python APIs for account/profile information to user_api
Updating profile page to have social linking

@stephensanchez @rlucioni @AlasdairSwan Please look over these changes.  Since this is behind a feature flag, we don't need this to be 100% complete, but the functionality we've implemented so far should work correctly.
From offline conversation: @stephensanchez noted that ugettext has a good way of dealing with multi-line messages built-in. However, since this copy could change (we still need approval from Product to use it), we'll hold off on i18n for the time being in an effort to avoid premature optimization. I'll add a note about i18n to the TODO.