config: add num-work-ids command line option

config: add num-work-ids command line option
Adds the parameter --num-work-ids to Options.py and reads the parameter
into the System params in Simulation.py. This parameter enables setting
the number of possible work items to different than 16. Support for this
parameter already exists in src/sim/System.py, so this changeset only
affects the Python config files.

Committed by: Nilay Vaish <nilay@cs.wisc.edu>