Updated mechanism for downloading Intel SGX DCAP driver on a VM that does not have the driver.
Change is as a result of a procedural change in the Intel release process.

Minor update to only install SGX driver if it is not already present in the image.

• Support new DC v2 hardware
• Pulls in latest Intel SGX DCAP driver
• Bug fixes

• added support for custom image URL
• added support to specify OS image from Azure Image Gallery
• added Windows provisioning
• added OpenSSH support on Windows
• added support for multiple SSH keys on Linux
• added passing public SSH keys from the command line
• added multi-VM deployment
• added configuration of DNS name for VMs
• added crontab job to rebuild SGX driver after kernel update
• added configuration of open ports in VM network security group

Single VM support