PCBC-206: Prototype for configuration caching

Change-Id: Id0ad0bfdd463f6e0c66f72aebc3fc0360972bbf6
Reviewed-on: http://review.couchbase.org/24881
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>