rest_topology: use decorator api

Signed-off-by: Satoshi Kobayashi <satoshi-k@stratosphere.co.jp>
Reviewed-by: YAMADA Hideki <yamada.hideki@po.ntts.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
wsgi: add ws_topology application

- Topology change is notified
  - JSON-RPC/WebSocket

Signed-off-by: Satoshi Kobayashi <satoshi-k@stratosphere.co.jp>
Reviewed-by: YAMADA Hideki <yamada.hideki@po.ntts.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>