[ADD] backport sepa direct debit

This is a backport of account_banking_pain_base, account_banking_sepa_direct_debit and account_banking_payment_export. Creating mandates and exporting payment order to PAIN works, but up to now I couldn't look into possible side effects of installing account_banking_payment_export
I'm refering the whole file. Sorry for not being too much clear. As you can see, the migration script is for 7.0 version.