Adds a Prepaid & Charge billing mode to carrier.account.mixin and
overrides the stock.picking method that sets the shipping cost on sales
orders after shipping. This modifies the behaviour of "invoicing policy"
on delivery.carrier when a delivery billing mode is selected on the SO
or picking.
When adding transport charges to a sale order via the "Add Shipping"
button, the line's description now contains the delivery billing mode
and account number when applicable.
Fixes#112
Add the ability to view all the transporter accounts from the sales
configuration menu.
Add company_id to delivery.carrier.account model as a related field
to delivery.carrier. Also constrain the delivery.carrier and res.partner
associated to an account to be linked to the same company.
Fixes#113
