Don't copy account transaction memo to bucket transaction memo

[flrns]

As a workaround, running

update bucket_transaction set memo=(select memo from account_transaction where id=bucket_transaction.account_trans_id)
where exists (select memo from account_transaction where id=bucket_transaction.account_trans_id);

on the sqlite-file will copy over all memos from account_transactions to bucket_transactions appropriately.

[iffy]

Related #738