- Don't use PowerShell to download WiX, instead just use HttpClient.
- Rehome WiX on our Azure blob storage, not only does this remove an
dependency of our build, it also fixes an issue where CodePlex 302's
from HTTPS to HTTP which HttpClient doesn't like.
- Bake version numbers into paths, to help in cases where we upgrade WiX
tool versions but the artifacts folder is not cleaned between builds.