Add Dockerfiles, plain Docker deployment instructions and minor fixes

Hi,

I've put all this in one PR, hope that's okay. It's basically what I had to change to get it working in my everything-is-dockerized environment.
I've tried to come up with "good commits". Let me know if you prefer single PRs for each of them.

So the idea here is to run kubernetes itself in Docker containers, therefor I created three Dockerfiles. The documentation assumes that this will be added as automated builds in the Google account. Guess that's up for discussion so let me know if I should change that.
The Dockerfile in / will create a kubernetes 'base image' which just includes the code/binaries and is used by kubernetes-node and kubernetes-server. This might not fit all all deployments but it's a good start and easy to understand.
To make this possible I added a `-docker` flag to point to the docker address (since with the bind-mount we can't use /var/run/docker.sock in the container). Beside that I made kubelet use the client lib for pulling the image instead of the binary (which isn't installed in the container).