Testing: Add account age verification scheme

[ManfredKarrer]

The feature is described here in details: https://github.com/bisq-network/proposals/blob/master/payment-account-age-witness.adoc

From the user perspective there is the account age displayed at the payment accounts, in the peer info (icon next to offer/trade) and in popups when a user tries to take an offer which cannot be taken because the taker has not reached the required trade limit by his account age.
The salt used for creating an account age witness can be transferred to a new application or payment account when using the same account data (e.g. IBAN).
The feature will be faded in over a few months period to avoid disruptions.

Testing that feature will be a bit difficult for non-developers and requires detailed understanding of the proposal. But doing trades with different account types (also multiple accounts with same payment method) will help to spot potential obvious bugs.