MDL-28452 core_user: migrate social profile fields

Create a new profile field type, move all existing content of the fields
'icq', 'skype', 'aim', 'yahoo', 'msn' and 'url' in the mdl_user table to
theses new profile fields if needed.

AMOS BEGIN
MOV [aimid,core],[aimid,courseimage,profilefield_social]
MOV [yahooid,core],[yahooid,profilefield_social]
MOV [skypeid,core],[skypeid,profilefield_social]
MOV [icqnumber,core],[icqnumber,profilefield_social]
MOV [msnid,core],[msnid,profilefield_social]
MOV [webpage,core],[webpage,profilefield_social]
AMOS END

lib/authlib.php

@@ -1200,8 +1200,6 @@ function display_auth_lock_options($settings, $auth, $userfields, $helptext, $ma
                 // limit for the setting name is 100.
                 $fieldnametoolong = true;
             }
-        } else if ($fieldname == 'url') {
-            $fieldname = get_string('webpage');
         } else {
             $fieldname = get_string($fieldname);
         }