* product.category: remove complete_name field as display_name can be used
where the field was used
* product.supplierinfo: remove computed qty field. This field originally
contained the min_qty computed into the product_uom. However commit
3c186c5807 broke that field without reason.
Since 2011 no one complained about this field being unnecessary, so let us
remove it.
* product.template: shorter and less spaghetti version of create_variant
method
* product_product._sellect_seller: fix use of default parameter in method
kwargs + use odoo standard datetime default value