Removing legacy operation classes & related code

Original goal of this MR was to modify legacy-serialization related code so that new operations don't have to be added to visitors like legacy_operation_conversion_visitor or convert_from_legacy_operation_visitor.
However the code analysis suggested that the legacy operations may be removed altogether which is demonstrated in this MR by removal of the most popular one - legacy_transfer_operation.
The next step was suggested to try removing legacy_signed_transaction.
EDIT: Now the MR includes removal of:

• legacy_signed_transaction
• each legacy_..._operation & related code
• handling of pre-rebranding calls and special error reaction

Also a quick fix to beem exception logging is included.