LU-11380 llapi: separate FID man pages

LU-11380 llapi: separate FID man pages

Add separate man pages for the lfs commands and llapi functions.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I05abfaf888a5474d62feebab4e8db543ba3ebbe5
Reviewed-on: https://review.whamcloud.com/35673
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>