Remove Twitter from SubMirror

Twitter removed Atom feeds in API v1.1, so there is no way to mirror
a feed without screen-scraping or registering a dev account with them.

plugins/SubMirror/forms/addtwitter.php

@@ -1,62 +0,0 @@
-<?php
-/**
- * StatusNet, the distributed open-source microblogging tool
- * PHP version 5
- *
- * LICENCE: This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- * @package   StatusNet
- * @copyright 2010 StatusNet, Inc.
- * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
- * @link      http://status.net/
- */
-
-if (!defined('STATUSNET') && !defined('LACONICA')) {
-    exit(1);
-}
-
-class AddTwitterMirrorForm extends AddMirrorForm
-{
-
-    /**
-     * Visible or invisible data elements
-     *
-     * Display the form fields that make up the data of the form.
-     * Sub-classes should overload this to show their data.
-     *
-     * @return void
-     */
-    function formData()
-    {
-        $this->out->hidden('provider', 'twitter');
-        $this->out->elementStart('fieldset');
-
-        $this->out->elementStart('ul');
-
-        $this->li();
-        $this->doInput('addmirror-feedurl',
-                       'screen_name',
-                       // TRANS: Field label.
-                       _m('Twitter username:'),
-                       $this->out->trimmed('screen_name'));
-        $this->unli();
-
-        $this->li();
-        // TRANS: Button text for adding a Twitter feed mirror.
-        $this->out->submit('addmirror-save', _m('BUTTON','Add feed'));
-        $this->unli();
-        $this->out->elementEnd('ul');
-        $this->out->elementEnd('fieldset');
-    }
-}