Skip extrapolation of missing core profiles

[eldond]

1. Make a list of profiles to extrapolate and loop through the list.
2. Test to see whether extrapolation is worth trying or if data are missing.
   • Avoids total failure when operating on reduced samples (sometimes we make file size smaller by deleting select fields from output; we don't need everything for every test)
3. Keep track of which profiles actually get extrapolated instead of skipped.
4. Report results, as in X/Y profiles were extrapolated.