pbs_snapshot --basic to capture minimal useful data

Motivation:

It's often useful to get basic configuration/state data from users to provide them suggestions on how to configure their system, and for internal testing purposes. pbs_snapshot today captures data in many different formats (e.g - multiple qstat & pbsnodes format), captures system data (like lsof, dmesg) and logs which can be time consuming and not necessary for such use cases. So, an option to capture only PBS configuration data would be useful for such cases.

External changes:

new option '--basic' for pbs_snapshot:
- Will capture only the following:
  - server/qstat_Bf.out - output of qstat -Bf
  - server/qstat_Qf.out - output of qstat -Qf
  - scheduler/qmgr_lsched.out - output of qmgr -c 'list sched'
  - node/pbsnodes_va.out - output of pbsnodes -va
  - reservation/pbs_rstat_f.out - output of pbs_rstat -f
  - job/qstat _f.out - output of qstat -f
  - hook/qmgr_lpbshook.out - output of qmgr -c 'list pbshook'
  - sched_priv/ for all sched instances
  - server_priv/resourcedef - the resourcedef file
  - pbs.conf - copy of server's pbs.conf
  - pbs_snapshot.log - log of pbs_snapshot execution
  - ctime - timestamp of when the snapshot was captured
  - job/qstat_tf.out - output of qstat -tf (this includes subjobs)
- Can be paired with other options like --accounting-logs & --daemon-logs to capture additional logging data if desired.