* element factory edded for doctrine forms

* some fields changed to optional

src/DoctrineExpressiveModule/Form/Element/ElementFactory.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace DoctrineExpressiveModule\Form\Element;
+
+use Interop\Container\ContainerInterface;
+
+class ElementFactory
+{
+
+    public function __invoke(ContainerInterface $container, string $elementClass)
+    {
+        $em = $container->get('doctrine.entity_manager.orm_default');
+        /** @var ObjectSelect|ObjectRadio|ObjectMultiCheckbox $element */
+        $element = new $elementClass();
+        $element->setOption('object_manager', $em);
+        return $element;
+    }
+}