Multiprocessing for job submission, event handlers, poll & kill.
Fixed missing import in cat-log command.
Fix task events test.
Got submit command working.
Restored simulation mode.
Removed some spurious line-end chars.
Corrected a shutdown test reference log.
Tidy suite shutdown.
Fixed database test

Comparison of db events with the reference version was failing on this
branch entirely due to a difference in event ordering, possibly because
"order by name, message" is ambiguous when only a few events recorded
messages?  Default ordering works on this branch and master.
Exit 1 on scheduler abort.
Fixed the state-dump tests and one restart test.

On this branch we exit from main loop immediately on shutdown instead of
going through the main loop once more (or partially) leading to minor
state differences at shutdown (e.g. ready vs waiting on shutdown -
the former triggers immediately on restart; the latter only after
prereqs are satisfied).
Single process pool for event handlers and poll-and-kill.
Simplified mp_pool.
Upped a test timeout.
Use common multiproc pool code.