Création de la classe Document parente de Invoice, Quotation et DeliveryNote

#161

common/models/DeliveryNote.php

  * @property string $city
  * @property string $postcode
  */
-class DeliveryNote extends ActiveRecordCommon
+class DeliveryNote extends Document
 {
     /**
      * @inheritdoc

common/models/Document.php

+<?php
+
+/* 
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+
+class Document extends ActiveRecordCommon
+{
+        
+}

common/models/Invoice.php

  * @property string $city
  * @property string $postcode
  */
-class Invoice extends ActiveRecordCommon
+class Invoice extends Document
 {
     /**
      * @inheritdoc

common/models/Quotation.php

  * @property string $city
  * @property string $postcode
  */
-class Quotation extends ActiveRecordCommon
+class Quotation extends Document
 {
     /**
      * @inheritdoc