Added reference to design docs from overview doc.

updated terminology, router is squashed into the projector.

Change-Id: Ibcedb78cf8448910f47b16aa37a524584e06c6ef
Reviewed-on: http://review.couchbase.org/34842
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Tested-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>