Add windows user SID as 'UID' in user resource. Fix #960

[ksubrama]

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[ksubrama]

PS C:\vagrant\code\inspec> bundle exec inspec shell -c "describe user('Administrator') do its('uid') { should_not eq nil
 } end"
[DEPRECATION] `script(script)` is deprecated.  Please use `powershell(script)` instead.
  ✔  User Administrator uid should not eq nil

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