AqBanking

Added virtual functions for online banking backends to provide some dialogs.

Added functions:
- AB_Provider_AddFlags()
- AB_Provider_GetNewUserDialog()
- AB_Provider_GetEditUserDialog()
- AB_Provider_GetNewAccountDialog()
- AB_Provider_GetEditAccountDialog()

git-svn-id: https://devel.aqbanking.de/svn/aqbanking/trunk@1863 5c42a225-8b10-0410-9873-89b7810ad06e