Better error handling in DCM UI

For some cases where disallowed or poor configuration causes unexpected behavior, the UI should give a visual indicator and explanation.  Two examples: 1. No write access for Relay to AF DB when using the PSC.  Result: replication of AF objects fails with many error messages.  Digging through log, found a message that indicated permissions issue on target AF DB.  In DCM, all was green. Would have been good to have an error or warning symbol on the Relay object with message about missing write permissions on Destination. 2. Added a second destination AF DB with reference to same Data Archive.  DCM showed red line on connection but no explanation; had to check logs.  Would be better to bubble the error message up to the UI so users don't have to switch windows.