Make GMapsDurationProcessor export unformatted data as
well, to enable later steps in the pipeline (such as filters) to
access and process this data.

You can't re-open a NamedTemporaryFile on Windows while it's still open.

This PR involves some refactoring. The problem is that previously,
filters ran before making any calls to external APIs. Therefore, just
adding another filter for the distance doesn't actually work: the
distance information is not yet available when we apply the filters. We
can't just run the filters later, because then we would run the Google
Maps API calls before we filtered out any properties, meaning that we
would incur Google Maps API calls for all properties that we find in our
search, including those that we later filter out anyway based on price,
size, etc. - and we actually have to pay for those requests! My solution
is to group the filters in two chains, and then run one chain before and
one after external API calls have been made. This way, we can run the
distance filter after the API calls are made, but keep everything else
the same.