Allow for custom error handlers for services
fix syntax regression of #375
fix unit test of #375
make latched_sub rostest independent from unit test execution order
Transport information in SlaveAPI::getBusInfo() for roscpp & rospy

- The information looks like 'TCPROS connection on port X to [Y:Z on socket S]'
- The information can be retrived by using getBusInfo() XMLRPC call to a roscpp/rospy nodes (added as an extra field to the end)
- UDP is not supported yet for rospy