ACE-626 allow OBR to report different base location

- allow the OBR servlet to be configured in what base URL it should use to
  report back to the client after handling a new uploaded resource. If no
  configuration is supplied, the "old" behaviour is used.



git-svn-id: https://svn.apache.org/repos/asf/ace/trunk@1802389 13f79535-47bb-0310-9956-ffa450edef68