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.
Again, just a design question. This creates a user, registers the user, then returns the activation key. In a second phase I'd be inclined to split up the user creation, return a user, then a separate function for registering the user. I.E.

registration_workflow()
   user = create_user(stuff)
   registery = register_user(user)
   return registration.activation_key

Just a nitpicky thought.