Adds support for a config-sets.yml file at the root path where named bundles
of app configurations (env, hooks, secrets) can be defined and activated
per-instance or per-group, eliminating duplication across instance configs.
- Config-sets are defined as top-level keys in config-sets.yml
- Activate a set in any instance or group alaka.yml with CONFIG-SETS: <name>: true
- Disable a set inherited from a group with CONFIG-SETS: <name>: false
- Merge priority: group < config-set < instance
- Warns when a config-set is enabled but not defined in config-sets.yml
- Warns when a config-set targets an app not listed in the instance config
- Adds examples/config-sets.yml with bbb and calendar config-set examples
