LU-930 utils: add --help option to lfs sub-commands

LU-930 utils: add --help option to lfs sub-commands

Add the "--help" and "-h" options to lfs sub-commands, and
print out an error message if an invalid argument is given.
Otherwise, it is possible to get a help message but have no
idea why the command is failing (e.g. typo in argument name).

Format the usage messages consistently, using {} to indicate a
choice between multiple required parameters, putting arguments
in [] for optional parameters, and using capitalized arguments.

Update respective man pages to list "--help|-h" option.

Remove the old SETSTRIPE and GETSTRIPE checks from spelling.txt
to avoid spurious checkpatch warnings.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ic583c8161d1d5380e353f43a8613dd86c93ebbe5
Reviewed-on: https://review.whamcloud.com/34659
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>