Frequent queries of status info

[LINGU2011-2012 (LINGU2)]

In some settings, we need to frequently query the status of a thinker. For example, the NGSCloud needs to know if a thinker is still running, and the thinker is behind a firewall -- the querying entity and the thinker are at different parts of the Internet. The current solution using SSH to periodically connecting into the thinker and running 'dt status' is quite iffy.

We'd better have a mechanism for efficient and reliable status query across the Internet.