Create azure VM cell image

Currently, we don't have azure counterpart for AWS AMI and GCE vm image. 
For alpha, creating such image manually should be fine; eventually we should have it automated in [kip-cell-image](https://github.com/elotl/kip-cell-image) pipeline. Here's [azure tutorial](https://docs.microsoft.com/en-us/azure/virtual-machines/linux/build-image-with-packer) how to automate it.