Format software instance JSON

Introduce a simple tool to format JSON for software instance definitions. This tool is inspired by python -m json.tool, but has the following differences:

• keep the order of keys instead of sorting alphabetically (because we sometimes put the most important options at the top)
• indent with 2 spaces

Run the tool on all the repository and commit the changes, with this command:

for x in $(find . -name '*.json') ; do  echo $x; ./format-json $x $x; done