impove dashboard and the default settings

[th-huber]

improve:

• The table "Kennzahlen nach Jahr" from DKP uses the date from the first payment, but the widget Verlaufstabelle in dkapp uses the loan.signDate

The default dasboard should

• be easy to understand
• contain the information from DKP's "Zahlen, Daten, Fakten" (the important numbers)
• showcast what's possible with widgets

Implementation

• Show important figures are at the top
• More advanced widget usage if the user scrolles down
• Remove median