[atlas] Categorize probes (feature request)

Hi!

Depending on the measurement, sometimes I want a realistic "user's view" 
which means using probes in residential areas, and sometimes I want a 
"backbone" view, which mean using probes in the back-bone (good 
connected) e.g. to measure my access network or my servers without the 
delay introduced by the probes access network.

Thus, it would be cool if the probe selection algorithm allows also to 
choose "residential" probes or "backbone" probes. Maybe this 
categorization can be done automatically, or probe owners can be asked 
to specify the probes connectivity manually.

Thanks,
Klaus