SW-826: adding Casacore.casa as dependency on LCS/Common makes many lofar libs dependend on 3rd party libs which we don't actually use. This hinders us in deployment and maintenance on various systems. Hence, I removed the hard dependency on Casacore.casa, and made the empty-stub-CasaLogSink print out a warning message.

Task #7756: LCS: improve thread-safety + clean up a few includes. All LCS tests pass + all MAC, RTCP, CEP builds ok.

First version