Implemented allow_unit_update in preorder

lib/mvcfronk/mfBase/mfBaseModel.php

@@ -223,6 +223,18 @@ class mfBaseModel {
       return "update";
     }
   }
+  
+  public function startTransaction() {
+    $this->db->query("START TRANSACTION");
+  }
+  
+  public function commitTransaction() {
+    $this->db->query("COMMIT");
+  }
+  
+  public function rollbackTransaction() {
+    $this->db->query("ROLLBACK");
+  }
 
   // generic functions for entity-classes
   public function toArray() {