[IMP] documentation and small cleanups
[IMP] rename standard_price to 'Inventory Value'.

Also simplified views by placing the cost_price always before standard_price.
Fixes #6
[IMP] translations (template+FR)

For some reason, the server seems unable to export the correct template for product_cost_incl_bom, so we'll use more context-neutral strings in product_get_cost_field and leave them unchanged in product_cost_incl_bom.