Use inverse video for bad pcal levels in monit6

Chris (Kokee) requested that inverse video be used for bad RDBE pcal levels in _monit6_. Mike (Westford) asked for this years ago, but unfortunately that request was lost in the shuffle (apologies).

Since what is bad may vary by station and IF, it would make sense to set the thresholds in _monit6.ctl_. If more granularity is needed later, that could be added too.