To handle the transition from ageRange to ageBuckets, export scripts
now support both, with a preference to ageBucket if that field exists.

There are three scenarios that are handled:

1. demographics.ageBuckets is present. This is the preferred option
   and the code sets the minimum and maximum of the buckets present
   as the age range

2. demographics.ageRange is present and the age window (difference
   between the maximum and minimum is at least MINIMUM_AGE_WINDOW

3. demographics.ageRange has a age window below MINIMUM_AGE_WINDOW.
   In this case the code matches it to the nearest age bucket(s).

Add index used by mongoexport in the export-data scripts

Also changes notify() to use the environment variable
PRUNE_UPLOADS_WEBHOOK_URL instead of using a parameter

export scripts should be deployed for both dev and prod. No
anticipated divergence is expected between them is expected at this
point, so deploying from main makes sense