Better dry run, improved execution messages, retrieve sensitivity indices.

- improve dry run functionality. Can now use dry run from the command line via the -d flag
- improve messages during exection. Add more details of what is currently being executed. 
  E.g., the command line used. Also save the messages to the output file under /output/jobs/n/stdout.
- Ability to retrieve the sensitivity indices using the hdf utility library (if available). The
  new function added is get_sensitivity with parameters identical to get_response.