Get-DiskByIdentifier: Allow selection based on Serial Number

[bozho]

Pull Request (PR) description

This PR introduces support for using disk serial number as a disk identifier in disk-related resources Disk, DiskAccessPath and WaitForDisk.

This Pull Request (PR) fixes the following issues

• Fixes Get-DiskByIdentifier: Allow selection based on Serial Number #259

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 the 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.

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This change is 

[bozho]

Need to add more tests

[PlagueHO]

This has been superseded by #271 .