Allow to create payments on quotes

The SaleQuoteWizard now has one more step: It allows to create payments
for the quote.

Those payments will be marked as pending so the user can mark them as paid
later (if they are really paid, obviously).

The SaleConfirmWizard is already prepared to take those payments in
consideration, so things should work out of the box there.

Change-Id: I1f208baf14d5a57353c7388877de4b0782b678f1
Merge "Allow to create payments on quotes"