Rename supplier_reference into reference

issue1479

view/purchase_form.xml

@@ -2,7 +2,7 @@
 <!-- This file is part of Tryton.  The COPYRIGHT file at the top level of
 this repository contains the full copyright notices and license terms. -->
 <data>
-    <xpath expr="/form/field[@name='supplier_reference']" position="after">
+    <xpath expr="/form/field[@name='reference']" position="after">
         <label name="customer"/>
         <field name="customer"/>
         <label name="delivery_address"/>