Modify a group management implementation with CBOR conversion in c stack

Modify a group management implementation with CBOR conversion in c stack

Previously, oicgroup.c file dealt with processing group action requests and
constructing the corresponding responses and it was strongly related with
json encoding/decoding. With this commit, all json-based codes in the file
have been updated to use CBOR instead of json.

Change-Id: I2f0953fab9c77024435d389538a4f43b600d7864
Signed-off-by: Jihun Ha <jihun.ha@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/2297
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>