Reject job at submit time if the node count is invalid

Previously such a job submitted to a DOWN partition would be queued.
bug 187
Purge vestigial job scripts

WIthout this patch, when the slurmd cold starts or slurmstepd
terminates abnormally, the job script file can be left around.
bug 243
Added support for FreeBSD.
Merge branch 'slurm-2.5'

Conflicts:
	doc/html/platforms.shtml
	doc/html/team.shtml