CMS-HLT-GPU Add output validation and smaller enhancements

This MR adds:

• output validation to the run script
• debugs, re-organizes, and hardens the config file copying and preparation, including the globaltag handling
• adds two new flags:
  • --debug: debug output enabled with the function cms_hlt_gpu_debug()
  • --keep_output: Prevents the cleanup of the CMSSW files from the output so that everything is written out -- WILL BE ADDED PROPERLY WITH THE NEXT MR (based on clean_work_dir)
• smaller refactorings and code improvements

This version was tested in 'cpu' mode and works as expected. The other modes will be tested and evaluated in a future MR.