Add ByteString support in CBOR wrapper in OIC stack

Add ByteString support in CBOR wrapper in OIC stack

Currently byte strings in CBOR wrapper are achieved by using
int arrays. Drawbacks with this approach is in-efficient memory
consumption and 3rd Party tools cannot properly decode the CBOR
generated in this fashion.

Updated code in CBOR wrapper and also added unit tests.

Change-Id: I4ed1adc891be84e800c833df404914a335150ded
Signed-off-by: Sachin Agrawal <sachin.agrawal@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/2337
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>