Windows 7 support

[obilodeau]

Note: This is a placeholder. We are not actively working on this. Contributions welcome!

We have a work in progress branch about this: https://github.com/GoSecure/pywsus/tree/win7_support

[obilodeau]

Instead of bundling the cab file (impossible due to licensing issues), @MaxNad suggested that we forward the request to the real WSUS server which is a great idea!

[MaxNad]

There are currently two problems with the Win7 support branch:

1. Distribution of the binary - We could forward the call to the actual WSUS server to bypass this problem. However, this should be a separate switch since providing the binary could still be used in cases where the server is unreachable.
2. HEAD request problem - While testing the branch, we have noticed that the client sometimes send a HEAD request and doesn't follow up with the download of the cab file. This issue should be investigated a bit more before the branch is merged.