Changing ocstack to retrieve double instead of int using cJson

Previously, we retrieved the sequence no. from presence payload
using object->valueint. Since the sequence no. is 32-bit unsigned
int, this caused the valueint to overflow. Hence, changing it to
object->valuedouble. This should fix IOT-549.

Change-Id: Idd30408c617e2ff84faa7c7c7f2a3f028577d337
Signed-off-by: Omkar Hegde <omkar.m.hegde@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/1245
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Erich Keane <erich.keane@intel.com>