Provisions for new node option NumberOfThreadsPerJob. Document option

This commit closes #1349 (closed). thanks a lot

@rattoma is there a reason to keep the commented code in 4ecf1d9f?

@houtanb the commented lines would be an alternative solution, should users report problems with the saved figures. The current solution should work, however. Perhaps we should add a note to the commented lines?

I just added a note to commented lines in 4ecf1d9f