Update status of EventMediator

[mchenggit]

Event Mediator needs to update status to at least reflect unsuccessful mediation calls
Need to keep in mind of frequency of status updates

[mchenggit]

Suggested approach:

1. Maintain per-destination list of error messages when making outbound call. (Can also track # of successful vs unsuccessful attempts.)
2. Maintain per-source list of error messages to track error processing for a source. Can also track # of successful vs unsuccessful messages and reason for failure, such as:
   • error from cel

• error calling outbound

3. Maintain error messages not associated with message processing, such as initialization errors

Also refrain from updating the status too frequently, especially if the error messages repeat.