Added fields to sepa direct debit list.

The new fields are:
 * creditor id
 * pain sequence type

See ISO 20022: http://www.iso20022.org/payments_messages.page

For now the pain sequence type is fixed to "RCUR" (should be "FRST" on initial
debit initiation).
Added date of mandate signing to payment info.

Schema change necessary:

ALTER TABLE members_paymentinfo ADD COLUMN
    bank_account_date_of_signing DATE
    AFTER bank_account_mandate_reference;
Updated mandate signing date to member details
Merge branch 'sepa_support_creditor_id' into django_1_5_compatibility