Added Device dashboard OC APIs

Added Device dashboard OC APIs

The apis in this change will be used to get complete state of
all the devices like owned/unowned status,device link status
and power on/off status.

[Patch 2] Updated code according to review comments.
[Patch 7] Rebase

Change-Id: If29a73646a4f77e4c6305de9ab4f3088a69a6eb7
Signed-off-by: Randeep Singh <randeep.s@samsung.com>
Signed-off-by: Woochul Shim <woochul.shim@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/2333
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Sachin Agrawal <sachin.agrawal@intel.com>