ePMP - add frame utilization to throughput chart

Being able to see frame utilization in somewhat realtime along with the throughput chart would be very helpful when watching busy APs.  

I currently use the excellent ePMP GUI+ chrome plugin but having to bounce back and forth between monitor->performance and monitor->throughput chart for some historical context is a pain.

we will consider this in the future

cnMaestro will track this historically for you.

If it can I can't find it, at least not for ePMP.  cnMaestro does track it for PMP450 though.