ceph.in: less verbosity on error

Only show 'did you mean?' when in verbose mode
Only show first ten closest matches on error

Signed-off-by: Dan Mick <dan.mick@inktank.com>
ceph.in: better global description of tool

Signed-off-by: Dan Mick <dan.mick@inktank.com>
ceph.in: allow args with -h to limit help to cmds that match partially

Enables "ceph -h pg" to see just the pg commands

Signed-off-by: Dan Mick <dan.mick@inktank.com>
Merge pull request #363 from dmick/wip-cli-help

Reviewed-by: Sage Weil <sage@inktank.com>