Make a combined JSON data file for all installers, shadow jar and JVL file for use in hugo.

The new hugo website likes to get data about stuff (in this case a particular version release of Jalview) from a data file, with one of the favoured formats being JSON.

It would be simpler and neater for website maintenance if there was one file for each release version. This means creating the installers, shadowjar, JVL file all in one go (not a difficult thing to do) so that the same build time appears in both jalview.jar and jalview-all.jar, and also the JSON file can be built up to contain information about every download file the website will want to know about (install4j installers, executable jar, JVL file).