AqHBCI: Restructured TAN entry code, removed unused functions.
TAN mechanisms have different interpretation of challenge and chellengeHHD,
the new structure takes this into account:
- replaced AH_User_InputTanWithChallenge() with AH_Outbox__CBox_InputTanWithChallenge()
- disabled AH_User_InputTanWithChallenge(), will be removed in next step
- introduced AH_TAN_MECHANISM which allows for handling of different
- added first implementation of AH_TAN_MECHANISM for "chipTAN optisch" (works!)
Removed some unused functions.