[IOT-1527] GroupManager according to the revised group resource model

[IOT-1527] GroupManager according to the revised group resource model

1. GroupManager to manage group management requests
  - GET oic/acl/group/<gid>
  - POST oic/acl/group/<gid>
  - POST oic/acl/group/<gid>?op=add
  - POST oic/acl/group/<gid>?op=delete
  - DELETE oic/acl/group/<gid>
2. User Authorization based group management

patch #28 #1: resources are not recorded to the group if devices regarding to the resources are already registered to the group
patch #28 #2: verification logic is added; when a device is registered to the parent group, recources of the device can be registered to subgroups

Change-Id: I5d90a0eea537e43fe06789db1897c90a766e01c4
Signed-off-by: yeonghun.nam <yeonghun.nam@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13609
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jee Hyeok Kim <jihyeok13.kim@samsung.com>