[IMP] website_sale: add multi image on product template.

addons/website_sale/models/product.py

addons/website_sale/models/res_config.py

addons/website_sale/security/ir.model.access.csv

addons/website_sale/security/website_sale.xml

addons/website_sale/static/src/css/website_sale.css

addons/website_sale/static/src/css/website_sale.sass

addons/website_sale/static/src/js/website_sale.js

addons/website_sale/views/res_config_view.xml

addons/website_sale/views/templates.xml

addons/website_sale/views/views.xml