Avoid slurmd fatal error with SlurmdUser!=root and env load

If a user job tries to load his environment remotely and the slurmd
is not running as root, the previous logic would generate a fatal
error, now it just logs the error and proceeds with the passed user
environment.
Add support for some new #PBS options in sbatch scripts

-l accelerator=true|false	(GPU use)
-l mpiprocs=#		(processors per node)
-l naccelerators=#	(GPU count)
-l select=#		(node count)
-l ncpus=#		(task count)
-v key=value		(environment variable)
-W umask=#		(set job's umask)