MB-100: log loaded replication documents

I.e. to make diagnosing issues like MB-9647 easier.

Change-Id: I35c5973367738a2c606b0812c4343e01d83b000a
Reviewed-on: http://review.couchbase.org/30879
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>