AqBanking: Added support for runtime config data (for FinTS registration).
For applications using FinTS/HBCI the German ZKA requiries applications
to be registered (see https://www.hbci-zka.de/register/prod_register.htm).
The registration key must somehow be passed from the application directly
to AqHBCI across interal layers which is normally not supported.
With this mechanism applications can provide some runtime data to AqBanking
(in this case the FINTS registration number) which is then picked up by
backends (in this case AqHBCI).
Runtime config data persists as long as the AB_BANKING object exists, so
applications should set the variables immediately after calling
AB_Banking_new() and before calling AB_Banking_Init().
For the particular case of providing the FINTS registration number the
following runtime variables are recognized by AqHBCI:
- "fintsRegistrationKey" (char): FINTS registration number
- "fintsApplicationVersionString" (char): major/minor version of the application (e.g. "1.2")