PowerShellGroup resource

[anmenaga]

PR Summary

Fix #48
Fix #72
Fix #79

PR Context

Added DSC/PowerShellGroup and DSC/WindowsPowerShellGroup resources.

Supported features:

• Class-based and script-based (MOF-based) classic PS resources

• Classic PS resource discovery:
  dsc.exe resource list

• Configuration Get/Set/Test operations:

Get-Content -raw C:\DSCv3\powershellgroup\testconfig1.yaml| dsc.exe config get
Get-Content -raw C:\DSCv3\powershellgroup\testconfig1.yaml| dsc.exe config set
Get-Content -raw C:\DSCv3\powershellgroup\testconfig1.yaml| dsc.exe config test

• Get/Set/Test operations on individual resources:

"{'Name':'PSGallery'}" | dsc.exe resource get -r PowerShellGet/MSFT_PSRepository
"{'Path':'./powershellgroup.resource.ps1','Ensure':'Present'}" | dsc.exe resource set -r TestFileDscResource/FileResource
"{'Path':'./powershellgroup.resource.ps1','Ensure':'Present'}" | dsc.exe resource test -r TestFileDscResource/FileResource

WindowsPowerShellGroup supports resource discovery using WindowsPS v5.1 and PSDesiredStateConfiguration v1.1 module; other operations will be added later. This is tracked by #87 .

[SteveL-MSFT]

a few more changes needed

[SteveL-MSFT]

LGTM