Data Analytics: Coin Discovery fix and update

[kolomaznikt]

At the moment, Coin Discovery event does not have a meaningful payload. It reports even unused empty accounts, and hidden accounts, meaning in case anyone enables btc, we discover at least 8 (2 for each of 4 different account types). Instead we should consider only accounts with some transaction history and count them once. Additionally, number of accounts with non-zero balance would be useful. So we would have:

• (old) parameter numberOfAccounts : now with only accounts with some transaction history counted once
• (new) parameter numberOfNon-zeroAccounts : with accounts with non-zero balance