Add option to show last transaction date in accounts

[gamue]

Closes #5556

Added functionality to the account-screen to show the last transaction date. This helps with keeping your balances up-to-date and potentially identify for which account you might need to recheck or add the transactions e.g. when having mutliple accounts that pay dividends or interests on a monthly basis, you can now see where you haven't added them yet.

Notes:

• I haven't adjusted the translations files yet as I first wanted to get the code and feature right. Also wondering about naming
• I thought the UI code was little bit hard to read, so I extracted it into smaller methods. Hope that's fine
• Unsure how testing works, I manually checked it (sorting; having accounts without transactions). Guess can for sure add unit-tests for getLastTransactionDate