Fast Model in LAVA

Support a Fast Model based virtual board in LAVA. Given a hardware pack and rootfs that are compatible with linaro-media-create, build a self contained Fast Model instance that boots the kernel, starts the rootfs, and then runs LAVA based tests similar to a real board.

Steps include:
 * Creating a rootfs in the correct format
 * Combining the boot-loader and kernel into the Fast Model boot format
 * Starting the Fast Model on demand
 * Communicating over the virtual console
 * Shutting down when a run is finished
 * Network access from the guest

The kernel will be KVM enabled.

This may be replaced by existing validation blueprints.