Windows.ps1 Cleanup

This is a variety of commits that do the following:

 * Update documentation for how to run from cmd.exe
 * Allow the puppet version to be specified to the script
 * Do not download the msi first, just pass it to msiexec
 * Do not install if already installed

With the not needing to download, this also allows someone to pass a local path or share to an internal MSI and it will just use it without error in an attempt to download the local file.


This also opens the door to have it ensure that the lowest version on the machine is the version requested, but it doesn't do that with this set of commits (and is part of the message after it ensures that Puppet is installed).