WindowsFeature: added Source parameter

[machgo]

Pull Request (PR) description

This PR adds the Source parameter back to the WindowsFeature-Ressource. This is needed for the installation of certain features, as example the .NET Framework 3.5 Features on Windows Server 2016.

This Pull Request (PR) fixes the following issues

-Fixes #150

Task list

• Added an entry under the Unreleased section in the CHANGELOG.md.
  Entry should say what was changed, and how that affects users (if applicable).
• Resource documentation added/updated in README.md.
• Resource parameter descriptions added/updated in README.md, 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.

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This change is 

[codecov-io]

Codecov Report

Merging #169 into dev will decrease coverage by <1%.
The diff coverage is 50%.

@@         Coverage Diff         @@
##            dev   #169   +/-   ##
===================================
- Coverage    83%    83%   -1%     
===================================
  Files        19     19           
  Lines      2760   2762    +2     
  Branches      4      4           
===================================
+ Hits       2303   2304    +1     
- Misses      453    454    +1     
  Partials      4      4

[gaelcolas]

Thanks @machgo for the added feature.
In theory we don't make much feature update or improvements to this module, as this is the supported replacement for in-box resources (so new features risks introducing new bugs, and the module HAS to be a like for like replacement).

In your case, the lack of tests might also be an issue, but the signature of the resource is backward compatible (no added key or mandatory parameter, not removed/renamed parameter).

While I double check with @kwirkykat, @mgreenegit or @mbreakey3 whether they want to accept this change, I'd recommend you open a similar PR to xPSDesiredStateConfiguration which would more easily bring such changes in.

[PlagueHO]

Hi @gaelcolas - did you get a chance to check with @mbreakey3 or @mgreenegit on whether we wanted to include this one?