New general configuration file parser and slurm.conf handling code.
Allows long lines to be continued on the next line by ending with a "\".
Whitespace is allowed between the key and "=", and between the "=" and
value.

slurm.conf is now read only once, and resulting data structures can be
shared between application and slurm library code.

WARNING: A NodeName may now occur only once in a slurm.conf file.
  If you want to temporarily make nodes DOWN in the slurm.conf,
  use the new DownNodes keyword (see "man slurm.conf").