Feature Request: Rule engine status available in MQTT & REST

[shabbab]

I just checked heishamon only to find rule to be inactive. Must have crashed at some point.

I think it would be nice to have a topic for the rulz engine status so some other process can send out a notification.

So a new MQTT topic holding info about the rules engine, something like:

• No rules defined
• Active
• Inactive, if possible including the error that caused this