Adds work_queue_enable_monitoring function.

This function replaces work_queue_create_monitoring. Instead,
work_queue_enable_monitoring is called with an existing queue.
Adds work_queue_enable_monitoring function.

This function replaces work_queue_create_monitoring. Instead,
work_queue_enable_monitoring is called with an existing queue.
Merge branch 'master' of github.com:cooperative-computing-lab/cctools
replaced "start byte" and "end byte" with "offset" and "length" for
all internal code referring to file pieces to reduce ambiguity.

This should fix bugs 1028 and 1029.