DSC meta configuration

[anmenaga]

PR Summary

Fix #282

This PR adds settings/policy JSON files support.
A particular dsc setting value (e.g. dsc resource search path) can be specified in any of the locations below.
Override order:

1. policy file. Writable only by Admins, but readable by everyone:

• on WIndows: $env:ProgramData+"\dsc\dsc.settings.json"
• on Linux: "/etc/dsc/dsc.settings.json"

2. command-line parameters. e.g. --trace-level or --trace-format
3. main active settings file: dsc.settings.json in dsc executable directory
4. default settings file: dsc_default.settings.json in dsc executable directory. Should not be modified by user and intended to be used in dsc upgrade scenarios as well as reset settings to defaults scenario. Top-level nodes in the file are versions of settings schema to support possible future breaking changes in settings schema.

Format and defaults for policy/settings currently look like this and described in detail in the spec:

{
  "resourcePath": {
    "allowEnvOverride": true,
    "appendEnvPath": true,
    "directories": []
  },
  "tracing": {
    "level": "WARN",
    "format": "Default",
    "allowOverride": true
  }
}

[michaeltlombardi]

To clarify, the scope of this initial PR is just to get DSC working with the settings/policy files, correct? The CLI / resource for getting and defining the values will follow in a future PR?

[anmenaga]

To clarify, the scope of this initial PR is just to get DSC working with the settings/policy files, correct? The CLI / resource for getting and defining the values will follow in a future PR?

Yes and Yes.

[SteveL-MSFT]

LGTM