product.py and product_views.xml contained code related to several models.
This commit split those files to separate submodels :
* decimal_precision
* product_attribute: product.attribute, product.attribute.value,
product.attribute.line
* product_template: product.template
* product_uom: product.uom and product.uom.categ
* res_currency
Product now contains product.product model, along with some smaller
models (product.packaging, product.supplierinfo, product.category,
product.price.history)
Thibault Delavallée