cbc: add switch --config-transport to choose HTTP/CCCP

Change-Id: I7eda1d684c1a5fd9bff13f27bdad2a1e804d27c8
Reviewed-on: http://review.couchbase.org/30865
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>