standardize job name, commands

[loriab]

two items for a standardization pass:

• (A) insofar as programs allow, should we standardize on a filename in qcng? e.g., qcengine_job.[in|out|inp|nw|mop] so it's clearer what are placeholders vs. runtime details.

• (B) commands and extra_commands are deceptive in that while one can have arguments aplenty, qcng.util.execute is adamant about running only one command. propose singularizing for clarity.