Improve "known balances" UX for synchronized bank accounts

[Bone008]

Most likely due to the discrepancy between "Buchung", "Wertstellung" and the internally assigned date, putting in known balances for bank accounts is a very painful experience, requiring manual checking of imported transaction dates and comparing them to what is shown in online banking.

Situations like this often happen:

Need to investigate deeper to find simple but more reliable solutions. One important component is most likely to take a different date column from the imported CSV row when calculating account balances.

[Bone008]

Another (UX only) problem is that transaction groups can make a bank transaction appear out-of-order with its physical date (e.g. if it was grouped with something far later).

While the code takes the correct date, the user cannot see this and currently has no way of listing "raw" transactions without grouping.