Configuration values need to be inserted to forms explicitly

It's the controllers' responsibility to ensure that forms are populated with
configuration values on GET requests.

refs #5525

library/Icinga/Web/Form.php

@@ -113,18 +113,6 @@ class Form extends Zend_Form
         return $this->tokenElementName;
     }
 
-    /**
-     * Return the current configuration for this form
-     *
-     * Intended to be implemented by concrete form classes.
-     *
-     * @return  array
-     */
-    public function getConfiguration()
-    {
-        return array();
-    }
-
     /**
      * Create and return the elements to add to this form
      *