Append session when forwarding payment requests
Remove whitespaces from account information in ParamBuilder

Users often enter their account information containing whitespaces, which is not allowed by the FinanceGate API.
Use correct shipping costs when building request to Payone's API
Transmit customernumber when creating API requests
Transmit correct vatid when creating API requests
Transmit no vat for articles to payone when the order is tax free

Squashed by @samuelvogel with "Fix wrong computation of tax free flag" from @stefanheppenheimer
Fix error in risk management