identify enabled/disabled accounts for windows

[chris-rock]

This PR adds a feature to the user and users resource to identifies enabled and disabled accounts. Usage examples are:

describe user('Administrator') do
  it { should be_disabled }
end

describe users.where { uid =~ /S\-1\-5\-21\-\d+\-\d+\-\d+\-500/ } do
  it { should be_disabled }
end

Further PRs will add that feature for other operating systems. That is tracked in #1040