Why no emulator image by default and how to get one

[anantshri]

Due to license issues and fact that download of images require a license to be accepted at sdk. Hence that's not done fromo ur end and is left for user to do.
Document should outline

1. why this is what it is
2. How to add emulators
3. caution while running emulator inside a VM and mitigations
4. how to connect

[anantshri]

How to add image is sorted.
5f929d4

We still need details on why we are not bundling SDK images with system.