LU-930 doc: man pages for lctl pool_new, pool_add

LU-930 doc: man pages for lctl pool_new, pool_add

Add man pages for lctl pool_new and lctl pool_add.

More pages are needed for other commands, pool_remove,
pool_destroy, and pool_list.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ie7cbb80d28610b9f74fe8f58c74c37a72e3ebbe5
Reviewed-on: https://review.whamcloud.com/34524
Reviewed-by: Joseph Gmitter <jgmitter@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Tested-by: Jenkins
Reviewed-by: Sergey Cheremencev <c17829@cray.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>