fastpath: add support for richer feature extraction

[hellais]

Extract additional features in the fastpath to make data analysis more powerful and the detection of censorship events more accurate.

A document which outlines some of the features we are interested in extracting can be found here: https://docs.google.com/document/d/1OI5msLwHkCFRsDBvdtUxSU7kelWiBlMFZ_TN2mcH7NE

• [ ] Extract more features
• [ ] Add 2-level classification e.g. DNS->nxdomain
• [ ] Add new columns to DB table
• [x] Modify fastpath or reprocessor to reprocess new msmts
• [ ] Perform table optimize to remove duplicates

The longer term plan is documented here: https://docs.google.com/document/d/1ahQRGQu7ASYmPjRwcRfXiQoDfk8YoMCm2IG-G8UzeJY/edit#heading=h.46xa7il1athv

[hellais]

This is mostly superseeded by the observation tables in ooni/data: https://github.com/ooni/data/pull/15

[hellais]

WRT to ISOC this is completed.