LUDOC-328 tbf: update TBF section to reflect the new changes

LUDOC-328 tbf: update TBF section to reflect the new changes

Update NRS-TBF policy section to reflect the following changes:
- change TBF command format, e.g. rate=<rate>, nid={nid},…
  - Lustre-commit: d09237044382361b289c01a9f7412818b3599e79
  - Lustre-change: http://review.whamcloud.com/19499
- specify ordering of TBF policy rules, e.g. rank=<rank>
  - Lustre-commit: aa14b0b9a1521b3deb26a07eb8f7bb28ce793001
  - Lustre-change: http://review.whamcloud.com/19476
- add opcode based TBF policy, e.g. opcode={opcode}
  - Lustre-commit: d2c403363f65337166dc745b58d0a4529a534b84
  - Lustre-change: http://review.whamcloud.com/11918
- support complex TBF rules, e.g. opcode={}&jobid={},nid={}
  - Lustre-commit: 949bc00ad1ec0786940bd00ba53479d88c23ea14
  - Lustre-change: http://review.whamcloud.com/17345
- support wildcard in JobID TBF rule, e.g. jobid={prog*.10*}
  - Lustre-commit: d5b5a07a8b07ab51a2215de593cb8bfce7e589d0
  - Lustre-change: http://review.whamcloud.com/24523

Change-Id: Iac8f735374cedf7065fdd445571fedcc01554d4c
Signed-off-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-on: https://review.whamcloud.com/30705
Tested-by: Jenkins
Reviewed-by: Yingjin Qian <qian@ddn.com>
Reviewed-by: Joseph Gmitter <joseph.gmitter@intel.com>