adopt changes from #156

[marqh]

This is a reworking of #156 It is intended to be exactly the same content.

This PR has 3 goals

• [x] manage the git history better, avoiding 'merge commits', which exist in the #156 history
• [x] separate the functional changes from the changes to the examples, putting these into separate commits
• run all the validation tests:
  • [x] on the functional changes, to demonstrate, on this ticket, that the previous examples would fail validation
  • [x] then run them again with the updated examples, demonstrating that the updated examples pass the validation tests

[marqh]

Thank you for the revised submission. May I suggest to copy the procedures mentioned in this PR onto a wiki page indicating best practices to help the team better manage this repository?

this is excellent advice, I have made a start on this guidance page: https://github.com/wmo-im/iwxxm/wiki/Guide-for-Maintainers

[blchoy]

Fantastic! May be you would also like to add a new bullet in between the second and third to elaborate your idea to separate functional and example changes into two commits to help readers better understand the changes? I think this is very important.