LU-1866 lfsck: general framework for LFSCK 1.5

LFSCK 1.5 main data structure definations, LFSCK
component APIs, setup/cleanup/start/stop interfaces.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I4507b9432289ca8d54cbf686893b706052d0eeb3
Reviewed-on: http://review.whamcloud.com/4908
Tested-by: Hudson
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>