Dsc_CMGroupDiscovery resource creation.

[jeffotterpohl]

Pull Request (PR) description

Adding additional functionality to to being able to manage GroupDiscovery within the resource.

This Pull Request (PR) fixes the following issues

Task list

• [X] Added an entry to the change log under the Unreleased section of the file CHANGELOG.md. Entry should say what was changed and how that affects users (if applicable), and reference the issue being resolved (if applicable).
• [X] Resource documentation added/updated in README.md.
• [X] Resource parameter descriptions added/updated in README.md, schema.mof and comment-based help.
• [X] Comment-based help added/updated.
• [X] Localization strings added/updated in all localization files as appropriate.
• [X] Examples appropriately added/updated.
• [X] Unit tests added/updated. See DSC Community Testing Guidelines.
• [ ] Integration tests added/updated (where possible). See DSC Community Testing Guidelines.
• [X] New/changed code adheres to DSC Community Style Guidelines.

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This change is 

[codecov[bot]]

Codecov Report

Merging #97 (9511258) into master (ee02d74) will increase coverage by 0%. The diff coverage is 100%.

@@          Coverage Diff           @@
##           master    #97    +/-   ##
======================================
  Coverage      98%    98%            
======================================
  Files          39     40     +1     
  Lines        5388   5653   +265     
======================================
+ Hits         5297   5562   +265     
  Misses         91     91