13 multi bank account support (#15)

* [13.0][IMP]add support for multiple bank accounts and multiple EBICS UserIDs over a single EBICS connection

* ebics refactoring fixes

* ebics refactoring fixes

account_ebics/migrations/13.0.1.1/pre-migration.py

@@ -0,0 +1,9 @@
+# Copyright 2009-2020 Noviat.
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+
+def migrate(cr, version):
+    if not version:
+        return
+
+    cr.execute("DELETE FROM ebics_xfer;")