Updated logic to create hierarchy in this form:

  EH/4/
      centre.json
          [55.96485,-3.2639]
      2.json
          {"AA":["55.9583","-3.2495"],"AB":["55.9589","-3.2508"],"AD":["55.9597","-3.2512"], ...}

  Creates 13704 files / 3003 directories.
  File size ranges from 13 bytes to 10k.
  Overall space claimed on disk: ca. 200MB.
  Time taken to generate files: ca. 1 minute.
Merge remote-tracking branch 'origin/master'