Couchbase-cli -h creates a lot of noise

Currently the CLI feels clumsy and noisy, and is not a pleasure to work with.

Ideally what should happen is that -h should be context specific to the command being given.

For example, if I was to run couchbase-cli -h then it should have the same output as without -h. However if I was to run couchbase-cli create-bucket -h, then it should show me the help output specific to that command.

I've had a look over the source code, and it would require probably around 4-8 hours of work to get it working. If a core contributor can provide some reassurances that such a PR would be accepted, and also some guidance on whether the suggested changes are acceptable, then I will happily contribute that time to get this done.

See also [here](1) for original discussion on forums.

[1]: https://forums.couchbase.com/t/couchbase-cli-h-creates-a-lot-of-noise/3572