Use libcouchbase for design doc management

Change-Id: Ic8bfa244ebabb1f3350a395a8c003229eedfed8e
Reviewed-on: http://review.couchbase.org/23916
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>