Operation history refactoring

[dr-orlovsky]

A new concept of operation history should be introduced.

Operation is a unit of accounting, providing related financial transactions as a single item.

Each operation may be related to a set o transaction outputs, including outputs from different transaction. A transaction may have outputs related to different operations. However, one output always connected to none or single operation.

By default, each non-change output of a new transaction should be used to construct a new operations.

Operations must have a separate list representation.