[FIX] point_of_sale: set back orders stat button

The stat button on the pos session that shows the different POS orders
linked to the session has been deleted by mistake in rev: 91532b7b

So we've set it back.

addons/point_of_sale/views/pos_session_view.xml

@@ -27,6 +27,12 @@
                 <sheet>
                     <field name="cash_register_id" invisible="1"/>
                     <div class="oe_button_box" name="button_box">
+                        <button name="action_view_order"
+                            class="oe_stat_button"
+                            icon="fa-shopping-basket"
+                            type="object">
+                            <field name="order_count" widget="statinfo" string="Orders"/>
+                        </button>
                         <button class="oe_stat_button" name="action_stock_picking" type="object" icon="fa-arrows-v" attrs="{'invisible':[('picking_count', '=', 0)]}">
                             <field name="picking_count" widget="statinfo" string="Picking Errors"/>
                         </button>