LU-2220 doc: add CLIO notes

LU-2220 doc: add CLIO notes

Add notes on the CLIO subsystem originally composed by Nikita Danilov
to the lustre/doc directory.  Update document to improve accuracy,
language, and formatting.

Original document URL:
http://wiki.lustre.org/images/3/37/CLIO-TOI-notes.pdf

Signed-off-by: Ned Bass <bass6@llnl.gov>
Change-Id: I18ac65bc437cf095ac7a897ebd2f8882318d27ad
Reviewed-on: http://review.whamcloud.com/4377
Tested-by: Hudson
Reviewed-by: Jinshan Xiong <jinshan.xiong@whamcloud.com>
Reviewed-by: Christopher J. Morrone <chris.morrone.llnl@gmail.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Tested-by: Ian Colle <Ian.Colle@intel.com>