Update role for windows

[Tyneven]

I make Pull request for update your role for windows part.

First, I fix some errors in variables names (The First Commit)
Second, I add requirements.txt to install netaddr to use ipaddr filter in your role and add 1 variable for Windows. (The Last commit)

Finally, In my case i don't use DSC on my Windows Server. (The penultimate commit)
I added check and conditioning for the installation of the Feature DSC.

Check if DSC Feature is installed on Server and Set fact
I leave dsc module only if DSC is installed on server and if Powershell version 5 or higher is installed on Server
I add win_feature module if DSC isn't installed and If the Powershell version is lower than version 5 on Server

[Tyneven]

In Last commit, i fix exceeded backslash for registry in Windows
I delete backslash and it works fine.

It's a fix like #21 Pull Request.

[Tyneven]

Hi,
Please, can have a return on this pull request? :)

[sbaerlocher]

Thanks for the PR.