Finance: Further improvements

[schmop]

The new Finance-Feature is missing some core elements. This is an issue collecting the features:

• Notifications (that you can deactivate in the settings) about new transactions in one of your households
• Instant Update by pushing into the SSE-Hub
• "Settle"-Buttons in the Overview for every Debt-Entry, that instantly creates the required Transfer to settle the debt
• Edit and Delete Transactions a short time after creation of the transaction.
  • But do not allow changes of long-existing transactions