Implement select(2) plugin

Change-Id: Ia7ca11cba8e69da4a5d4fc7c1b09fb328f903287
Reviewed-on: http://review.couchbase.org/27516
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>