xWebAdministration: Moved PHP example from README.md into its own example file

[vikingtiger]

Pull Request (PR) description

The PHP example was moved from README.md into its own example file under the /Examples directory.

This Pull Request (PR) fixes the following issues

• Fixes #485

Task list

• [x] Added an entry to the change log under the Unreleased section of the CHANGELOG.md. Entry should say what was changed and how that affects users (if applicable), and reference the issue being resolved (if applicable).
• [ ] Resource documentation added/updated in README.md.
• [ ] Resource parameter descriptions added/updated in README.md, schema.mof and comment-based help.
• [x] 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 

[msftclas]

All CLA requirements met.

[codecov-io]

Codecov Report

Merging #539 into dev will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev     #539   +/-   ##
=======================================
  Coverage   91.72%   91.72%           
=======================================
  Files          17       17           
  Lines        2766     2766           
=======================================
  Hits         2537     2537           
  Misses        229      229

Impacted Files	Coverage Δ
DSCResources/MSFT_xWebSite/MSFT_xWebSite.psm1
DSCResources/MSFT_xWebsite/MSFT_xWebsite.psm1	97.22% <0%> (ø)

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