Implemented WWFee

[arisb1470]

• Check if you can navigate back to "Finanzübersicht" with the button "zurück". Check if all the TextFields are filled in by default. "Ausführungsdatum" should be filled in with a date that is 19 days from now. You should still be able to edit all text fields. Check if the input restrictions for the payment amount is working correctly.
• Check if the table is shown correcty.
• Check if the filters and sorting by name is working.
• Check if the "SEPA-XML ERSTELLEN" button is working correctly. It should open a dialog that changes dependent on which radio button is selected.
• Check if the radio buttons are shown correclty, each member should already have a radio button checked. You should be able to select any radioButton. If you want to check if the values for the payment amount are working correctly, you can add this to the SEPA-XML ERSTELLEN button: "console.log(selectedAmounts);"

[LennartRukower]

Very good work!

What I asked myself is the following: When changing the amount someone has to pay, then it is saved into the db immediately (which makes sense). But maybe there should be a button, that retrieves the calculated values again, if someone makes a mistake. What do you @ChristianObst, @jbt-it think?

@arisb1470, your PR is fine. Good work!