[Observium] Freeradius app patch

Hi,

I did some work for adding support for freeradius. You may find the patch at the following url:

http://master.math.upatras.gr/~hasiotis/freeradius-app.diff

It's working but It may need improvement on the way graphs are rendered. Please feel free to add to observium if you like it.

Thanks

-- Nikos