The OAuth code was moved to the adal package.
Authorizers now ues an interface instead of a simple token.
Long running operations return a channel for the operation, and the
error.
This is last merge that will happen from the github.com/Azure/packer-Azure
repository. All development is being over to this repository.
The biggest change in this merge is support for Windows. There are a few other
fixes as well.
* If the user cancels the build, clean up any resources.
* Output a reasonable build artifact.
* Log requests and responses with Azure.
* Support for US Government and the China clouds.
* Support interrupting long running tasks.
* Allow the user to set the image version.
* Device login support.