Task SW-516: Change all hashbangs from pointing to python2 or default python to python3

CEP/Calibration/BBSControl/scripts/addClearcalColumns.py

CEP/Calibration/BBSControl/scripts/addImagingColumns.py

CEP/Calibration/BBSControl/scripts/casapy2bbs.py

CEP/Calibration/BBSControl/scripts/checkBBSskymodel.py

CEP/Calibration/BBSControl/scripts/parmdbplot.py

CEP/Calibration/BBSControl/scripts/plotcorrmatrix.py

CEP/Calibration/BBSControl/scripts/plotexport.py

CEP/Calibration/BBSControl/scripts/plothistogram.py

CEP/Calibration/BBSControl/scripts/plotwindow.py

CEP/Calibration/BBSControl/scripts/solverdialog.py

CEP/Calibration/BBSControl/scripts/solverexport.py

CEP/Calibration/BBSTools/scripts/BBStiming.py

CEP/Calibration/BBSTools/scripts/testbbs.py

CEP/Calibration/BBSTools/scripts/testdppp.py

CEP/Calibration/BBSTools/scripts/testsip.py

CEP/Calibration/ElementResponse/src/convert_coeff.py

CEP/Calibration/ExpIon/src/MMionosphere.py

CEP/Calibration/ExpIon/src/calibrate-ion

CEP/Calibration/ExpIon/src/ionosphere.py

CEP/Calibration/ExpIon/src/parmdbwriter.py