RCAS.py: simplify arguments for switching on/off optional steps
RCAS.py: simplify arguments for switching on/off optional steps

BIMSBbioinfo/RCAS-tools,dyusuf/RCAS,BIMSBbioinfo/RCAS-tools,dyusuf/RCAS,BIMSBbioinfo/RCAS-tools,dyusuf/RCAS