The "show unknown events" checkbox on the events monitoring page

The label "Show uknown events" is imprecise, because when it's unset, we also don't display insignificant PROBLEM and OK events.

It's really confusing. I opened the events page, saw a whole bunch of PROBLEM and OK events and a few UKNOWN events. I've unchecked the checkbox and all of the events have disappeared. It took a while to figure out, that all of these events where just insignificant. I think it would be better to rename the checkbox to something like "Show insignificant events".