When you have no alerting rules defined you get a screen sharing this
information in the WebUI. If no rules are defined then you instead see
an empty white screen. This adds a "No rules" defined `else` clause and
a `Rules` header to the page.
I got feedback from different sources about rules and targets being
too heavy in the status tab if their are lots of them.
This change also allows for more fine-granular locking.
