Change Secondary Key format for composite keys

Use the two-dimensional format for composite secondary keys
for the first integration.

Change-Id: I48e1a4bfb73cba0aeb54d63f7d2671a82e662061
Reviewed-on: http://review.couchbase.org/38493
Reviewed-by: John Liang <johliang00@gmail.com>
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Tested-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>