fix namedtuple in csv reading, and move strip logic to feed.py

The csv output was replaced to namedtuples by @eoghanmurray in
49c20747db88e7e218fb4fc83b61fbc0b37f552d . However load.py was not changed,
and therefore remained incompatible. This is solved here.

Also, the field strip was moved from load.py to feed.py and is
done in an earlier stage.