authorize Facebook application from user profile page

Display Facebook account data to WordPress users with `edit_posts` capability or prompt the user to associate his or her WordPress account with a Facebook account with `publish_stream` scope if connection is not already active and permissions not present.

Link to App Settings section of Facebook.com settings for permissions management after authorization.

Allow a WordPress user with an associated Facebook account and granted `publish_stream` permission to disable posting to Facebook through a checkbox on his or her profile.