ExecutionLogEntry_copyToOutbox
This contributes a copyToOutbox action to each ExecutionLogEntry (from the Execution Log extension) so that it can be republished in the outbox.
This is useful when both the Execution Log and Execution Outbox extensions are in use, and there was a downstream problem with the processing of an execution from the outbox ; the mixin takes a copy of that execution from the log and copies it to the outbox in order that it can be reprocessed again.