CCBC-439: Provided better help text/usage for cbc subcommands

This adds some subcommand help by using --help

Change-Id: Ic6f67ac9fdaddc37028d3518dbc6a3b06bddc4a0
Reviewed-on: http://review.couchbase.org/41195
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>