Streaming should send keep-alive signals to Reporter

The goal is to avoid the 10-minutes Task timeout with certain usages of hadoopStreaming.

This proposal does not introduce an artificial keep-alive heartbeat:
it still requires the external Application to have activity.

Streaming should set Reporter status in more places:

1. output to side-effect files should (periodically) set reporter status.

2. Application's stderr data should (periodically) set reporter status.