fix launchGuy for non interactive use (at, batch, slurm,...) by replacing '*Guy.pyw' by '*.py' in runBatch, runSge, runSlurm,... I also add a test to not close the gui when launching a nonInteractive job

replace distutils.spawn.find_executable(...) (that does not work with .bat, .cmd,... files) by shutil.which(...)

fix the use of scilab.bat as a scilab launcher and replace find_executable by which in checkValidity