PCBC-210 - Add default entry for loading the extension

Change-Id: I5ccbb20d1c6ae53a0b91ff4d556cf1ca675b0730
Reviewed-on: http://review.couchbase.org/25052
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>