Candidate FPWD of CoverageJSON document for discussion in London

Hi all

Jon Blower and I have made a number of updates to the CoverageJSON
document: see http://w3c.github.io/sdw/coverage-json/ and
https://github.com/w3c/sdw/tree/gh-pages/coverage-json

There are still a lot of 'TO DO' sections in it, but the main structure and
a large part of the content is there.

Our intention is to replace the TO DO bits with real text of course.  We'd
welcome feedback on the material that is there and also guidance on how far
we need to get with the TO DOs before it is suitable for FPWD.

Also, a significant question still to resolve is whether to incorporate the
full spec in this document or not.  Jon has raised a few questions with
Phil on that and we can discuss further in London.

Best regards

Bill