Errors creating destinations are now reported
Queue messages on dead destinations
Log Destination Startup Errors.

Moved pre 0.3.0 channel support out of _loadChannels into its own
function to be removed in 0.4.0.
Remove SourceConnector, Add DestinationConnector.

At some point, what source connector was doing was duplicated in
connector. Removing it.

Channel is doing too much connector-specific work. This splits all of that
out into the new Destination Connector.