Add VAT taxes for uses on products bought as long term assets

They have a dedicate tax code on the VAT declaration and we thus need
separate taxes.

issue4108
review9551002
Switch some asset accounts to kind=expense

This allows us to create products that can be bought and then managed as
assets because they are expensive and should amortized.

We do this only for asset accounts that are likely to hold regular products
of suppliers.

issue4110
review5501002
Create 646* accounts mimicking 645* accounts

We need the same set of sub-accounts except 6464 which concerns only
employees and not the company owner.

issue4111
review10471002