Extend suggested feeds to include users who have opted in to share their phone numbers.

• Extend the user entity to have a flag that indicates they have opted into find a friend feature
• Provide an endpoint for mobile clients to upload their address books
• Create a user lookup schema that associates hashed phone numbers of friends with a user's guid
• Extend the suggested channels endpoint to include the channels of users who have opted in and have matching hashes of the phone number.

bold need to verify that we can match phone numbers in one way hashing, that way we can find matches without compromising anyone's private information