Added a User_username table that links the external username with a StatusNet user_id

Added EmailAuthenticationPlugin
Added ReverseUsernameAuthenticationPlugin
Changed the StartChangePassword and EndChangePassword events to take a user, instead of a nickname
User::allowed_nickname was declared non-static, but used as if it was static, so I made the declaration static

lib/util.php

@@ -1058,6 +1058,7 @@ function common_log($priority, $msg, $filename=null)
         }
     } else {
         common_ensure_syslog();
+        error_log($msg);
         syslog($priority, $msg);
     }
 }