Task #4421: Changed location of pipeline logs to /opt/lofar/var/log/pipeline-ObservationXXXXX-TIMESTAMP.log

This patch works around the C++ side of MessageBus where XML encoding of special chars
is not done, or perhaps not done if libxml++ is not built.
It'd be better to fix the C++ side than to refrain from encoding on the python side in even
murkier situations, but MessageBus is deprecated and I've spent enough time trying to fix it.

Testing: All MessageBus tests pass on cbt009.

Task #8809: update commented-out filename in CMakeLists.txt for ObservationStartListener systemd service file

Task #8832: Removed trunk directory from the trunk, which must have gotten in by accident when branch LOFAR-Task8832 was created.