Add Shutdown API

[mukundansundar]

Describe the proposal

With the addition of the shutdown API in proto https://github.com/dapr/dapr/blob/master/dapr/proto/runtime/v1/dapr.proto#L82
and HTTP https://github.com/dapr/dapr/blob/master/pkg/http/api.go#L316-L325
add a shutdown API in Java as well

• gRPC and HTTP API
• Unit Test
• Integration Test
• Example?