Issues 22646, 22647, 22648 data-in-modules simplification

This contains fixes for Redmine issues 22646, 22647, 22648
* Simplify hiera.yaml and binder_config.yaml
* Add smart defaults
* Support private / nested hierarchies

The boundaries between the issues somewhat blurred, all commits marked with 22646.

Overview of what the simplifications are is found here: https://github.com/hlindberg/misc-puppet-docs/blob/master/improvements-arm-9.md