Update Consumer C APIs.

Update Consumer C APIs.

1) Parameter as NSProvider structure is changed C string providerId.
2) NSTopicLL is seperated from NSProvider structure.
3) Topic releated API is renamed and changed return type.
4) NSUnsubscribe API is commented out.

Conflicts:
        service/notification/examples/linux/notificationconsumer.c

Change-Id: Ib46ed952cdab58cb9f95eaeb4e405b7da4adeb2f
Signed-off-by: KIM JungYong <jyong2.kim@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/11335
Reviewed-by: Uze Choi <uzchoi@samsung.com>
Tested-by: Uze Choi <uzchoi@samsung.com>