Ensure LOFAR utitlies are pip-installable

This minor release ensures that the LOFAR utilities are pip-installable. A warning is issued when "old-school" python setup.py is used instead of pip.

To install the LOFAR utilities and its dependencies (except those on lofar.parmdb), use pip install RMextract[lofar-utils], or if you already have a copy of the source tree, you can use pip install .[lofar-utils], instead of python setup.py install --add-lofar-utils.