Clarify meaning of CPU in a FAQ
job_submit/lua - add cpus_per_task field

bug 511
document performance issue for shared=yes|force

The time/resource allocation matrix is rebuilt on each job
exit, which severely impacts performance at large counts of
running jobs (say >10k jobs).
Merge branch 'slurm-2.6'

Conflicts:
	doc/html/faq.shtml