https://issues.apache.org/jira/browse/AMQ-5395

Check for the presence of a prefix before asking for a substring
Remove unused imports
https://issues.apache.org/jira/browse/AMQ-5391

Allow for an anonymous relay using a configurable node name when
creating the new link, default is $relay.  Message's that arrive without
a to field set are rejected as this is required for a relay.