Add script to provision closed beta VM

This MR:

• enables the VNC connection on created VMs (since we'll need to leave a UI login session open so that users can run UI tools like the iOS simulator).
• adds scripts/closed_beta/create_env to have a single script to create a VM and register the Runner for a closed beta user (assumes that the user has been created already)
• updates the documentation

Closes #34 (closed)