Rename imported_data_mapping table to mapping_to_external_entities

lib/Models/MappingToExternalEntities.php

@@ -0,0 +1,15 @@
+<?php
+namespace MailPoet\Models;
+
+if(!defined('ABSPATH')) exit;
+
+class MappingToExternalEntities extends Model {
+  public static $_table = MP_MAPPING_TO_EXTERNAL_ENTITIES_TABLE;
+
+  static function create($data = array()) {
+    $relation = parent::create();
+    $relation->hydrate($data);
+    return $relation->save();
+  }
+
+}