Form: Define classes `icinga-forms` and `icinga-controls` by default

library/Icinga/Web/Form.php

@@ -32,6 +32,11 @@ class Form extends Zend_Form
      */
     const DEFAULT_SUFFIX = '_default';
 
+    /**
+     * A form's default CSS classes
+     */
+    const DEFAULT_CLASSES = 'icinga-forms icinga-controls';
+
     /**
      * Identifier for notifications of type error
      */
@@ -239,6 +244,10 @@ class Form extends Zend_Form
             )
         ));
 
+        if (! isset($options['attribs']['class'])) {
+            $options['attribs']['class'] = static::DEFAULT_CLASSES;
+        }
+
         parent::__construct($options);
     }