LUDOC-85 enhance: new LFSCK options are now documented.

LUDOC-85 enhance: new LFSCK options are now documented.

LFSCK has added significant functionality in the recent release. The
manual now makes a clear distinction which version of lustre supports
the various lfsck options.

LFSCK namespace is now included and documented.

Signed-off-by: Richard Henwood <richard.henwood@intel.com>
Change-Id: Iff0ff5b696b8a55fefedfcfe78031e28c2a93749
Reviewed-on: http://review.whamcloud.com/5801
Tested-by: Hudson
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Cliff White <cliff.white@intel.com>