POS Second EAN13

This module adds a second EAN13 field on products. This feature has been asked by librairies that often have the same book available from 2 different sources with different EAN13 (to keep things simple, I didn't want to handle N EAN13 ; a second EAN13 was enough for most cases). This module also provides a patch to apply on the source code of Odoo (file patch-point_of_sale-second_ean13.diff) : this patch modifies the javascript code of the official point_of_sale module of Odoo.

I recommend to also install the module pos_no_product_template_menu because the second EAN13 is only shown in the product.product form view (I don't want to add the hack to have the second EAN13 field on product.template form view, in order to keep this module as simple as possible).

This module has been written by Alexis de Lattre from Akretion <alexis.delattre@akretion.com>.