Removed autologin functionality from springboard_cookie.module. Too dangerous to let anyone log in as user@example.com just by submitting a petition or donation form with that email.
Added springboard_cookie_init() logic to create a new user account when an "sbck" query string parameter decrypts to an email address for which no Drupal user account exists.
Added a hook_springboard_cookie_uid invocation to springboard_cookie_tag_client(), so modules can know when a uid is added to a client cookie that didn't had one.
Added hook_springboard_cookie_uid() implementation to sb_social.module, so when a client cookie with share_ids gets a uid added, those shares get updated (and put in the SF queue) with that uid.