Add script to generate schedule for release.gnome.org, and remove the wiki schedule script
This produces almost the same output as the existing r.g.o json calendar, with only a few changes:
- The newstable.0 release sorts after 46.5 and 45.10 instead of above them.
- The newstable.0 release has a release_date property instead of a release-date property, since the hyphen looks like a typo.
- The newstable.0 release grows a soft_translation_deadline property.
- I've removed the trailing .0 from the version numbers of previous releases, since we show only the major releases here.