Fix some string used for group management feature

Fix some string used for group management feature

1. Instead of "oc", "oic" is used for decoding a JSON request in group management.
2. There are a difference of group interface string in octypes.h and ocapi.h.
   "oic.mi.def" will be used in the both.

Change-Id: I79763315926dc6e6bba3444db5ed94a68db65eb2
Signed-off-by: Jihun Ha <jihun.ha@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/1527
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>
Reviewed-by: Junghyun Oh <junghyun.oh@samsung.com>
Reviewed-by: Patrick Lankswert <patrick.lankswert@intel.com>