Improve network_type annotation

[agrabeli]

During the OONI Partner Training 2021, participants mentioned that it would be helpful if OONI measurements characterized the AS networks (wifi, mobile data, University network, etc.).

[hellais]

I am not sure it's feasible to do this at AS level granularity. Many ASs will have both fixed and mobile networks, while universities may use as upstream a network which is also used in non-university context.

For distinguishing between wifi and mobile the detection is already done on the probe side (and flagged via the network_type), while for characterising the type of organisation that the network is run by (ex. university or corporate office) I think this should be done by the user.