GH-554: add PaymentAdjuster without the smart interior

[bertllll]

Ranks under this mother card #GH-554

Straight continuation of #GH-671.

Base end implementation which enables payment adjustment suggested by #GH-554 come in effect.

The PaymentAdjuster should compose one of the parts of Accountant. Its role is to be asked for help if Accountant receives a special message from BlockchainBridge that carries information about the consuming wallet balances (of the token -- but contains also information about the gas currency) whilst the token amount reported wouldn't be enough to pay off all the debts that have qualified within the scan. Accountant, who finds this out, would then pass this difficulty to PaymentAdjuster expecting it to solve that for him and give the payments back, properly adjusted to such partial token amounts that can all go to BlockchainBridge and can all be paid without lacking any means to do so.

In this card prepare just some fundamental infrastructure containing already the new PaymentAdjuster but yet not giving the desired intelligence inside. That part should be done in a separate card as it might require a lot of design work and testing.

[bertllll]

Planned schema

Brainstorming2.odg