Proposal for enhancing historical information of Operations in FireFly for DX and other plugins

When data exchange events are received, they contain additional information under the "info" JSON object. Within a single operation there may be more than one data exchange event. Currently, when a new data exchange event comes in for an operation that already had a previous data exchange event, the "info" JSON object is overwritten. The logic should be changed in order to aggregate these objects as it will be important to see what that information was throughout the operation and in each of the data exchange events. More information can be found in https://github.com/hyperledger/firefly/pull/534#pullrequestreview-886324831