Provide bucketless bootstrap for libcouchbase 2.x

Currently, it is necessary to specify the bucket name as part of connection string - https://github.com/couchbase/libcouchbase/blob/master/example/minimal/query.c#L133

This makes it impossible for writing applications where we are just given a query, without any information about the buckets in the cluster and are required to execute the query.

This blocks us from integrating N1QL support in js-evaluator.