(model, fieldtypes) add update only text field type, closes...

(model, fieldtypes) add update only text field type, closes https://github.com/opnsense/core/issues/1045

src/opnsense/mvc/app/models/OPNsense/Base/FieldTypes/UpdateOnlyTextField.php

+<?php
+/**
+ *    Copyright (C) 2016 Deciso B.V.
+ *
+ *    All rights reserved.
+ *
+ *    Redistribution and use in source and binary forms, with or without
+ *    modification, are permitted provided that the following conditions are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright notice,
+ *       this list of conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *
+ *    THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ *    INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ *    AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ *    AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ *    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *    POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+namespace OPNsense\Base\FieldTypes;
+
+use Phalcon\Validation\Validator\Regex;
+use Phalcon\Validation\Validator\PresenceOf;
+
+/**
+ * Class update only TextField (can be practical for password type fields)
+ * @package OPNsense\Base\FieldTypes
+ */
+class UpdateOnlyTextField extends TextField
+{
+    /**
+     * Always return blank
+     * @return string
+     */
+    public function __toString()
+    {
+        return "";
+    }
+
+    /**
+     * update field (if not empty)
+     * @param string $value
+     */
+    public function setValue($value)
+    {
+        if ($value != "") {
+            parent::setValue($value);
+        }
+    }
+}