Add reference to .net4 & update wsus content dir

[techspence]

This pull request is to:

1. Add a reference and link to .NET 4.0 in README.md
2. Pull the WSUS Content Directory location from the SQL database instead of the registry. In my testing, the registry path was one folder higher than where the patches get downloaded to. This results in the payload failing to download until it's in the correct folder.