fixed dbo to json

src/Generator/dbo.php.twig

@@ -8,7 +8,11 @@ class {{ dbo_name.camel_upper }} extends LuDbo {
 
     public function jsonSerialize()
     {
-        return $this->__toString();
+        return array(
+{% for column in columns %}
+            "{{ column.name.camel_upper }}" => $this->_{{ column.name.camel_lower }}{{ loop.last ? "" : "," }}
+{% endfor %}
+        );
     }
 {% for column in columns %}