* Match machines to their Ignition template file, render the
template, parse as JSON or YAML, and serve as Ignition JSON
* Existing JSON ignition configs should still work
* Remove the Ignition YAML -> JSON transform script which used fuze
* Use YAML group config to match machine labels to groups of zero or
more machines sharing a Specification
* Discontinue using machine.json resources representations which are
repetitive, don't support groups, and don't allow label matching
* Previous "default" special case now handled by a Group with an empty
matcher
