automate accounting for acceptance points

[brenzi]

includes:

• indexing of all balance-relevant events (transactions, ceremony rewards, demurrage)
• preparing of monthly statements

a monthly statement should include:

• Einkünfte einzeln und total
• Ausgaben einzeln und total
• Saldo per Anfang und Ende Monat

Special care needs to be taken to CCI:

• CCI reward issuance did not trigger an event for each account before runtime v8 (before Aug 15th: https://encointer.subscan.io/extrinsic/1068966-0?event=1068966-0)
• this means we need to hand-insert CCI issuance or the saldo will not be correct
• from runtime v8 onwards, we should be able to derive all balance changes with the following events:
  • encointerBalances.Transferred
  • encointerBalances.Issued