Add simplistic qemu - trying out the driver model refactor 

its aweful, non-persistent, and none of the commands are implemented.

but. If you `boot2docker-test-linux-amd64 --driver=qemu --iso=/home/sven/.boot2docker/boot2docker.iso up`

then it will boot with the vm's console in the current terminal.

I quit by hitting `ESC-2` and typing `exit` on the qemu console.

very useful for testing :)