Added Comment Based Help for New-NotImplementedException - Fixes #411

[PlagueHO]

Pull Request (PR) description

This PR adds missing comment based help to New-NotImplementedException function.

This Pull Request (PR) fixes the following issues

• Fixes Common Function New-NotImplementedException Missing Comment Based Help #411

Task list

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

@johlju - would you mind reviewing for me?

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This change is 

[codecov-io]

Codecov Report

Merging #412 into dev will not change coverage.
The diff coverage is n/a.

@@         Coverage Diff         @@
##            dev   #412   +/-   ##
===================================
  Coverage    95%    95%           
===================================
  Files        28     28           
  Lines      2272   2272           
===================================
  Hits       2172   2172           
  Misses      100    100

[johlju]

Reviewed 2 of 2 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved