[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 believe you are correct. It did not use to be the case but I think the problem is that the web module triggers the loading of every module in the addons path with a static folder in it (if only containing a logo icon, like this module).