Add version information for components we depend on.

Sample output:
Version: {KernelVersion:3.11.0-17-generic ContainerOsVersion:Ubuntu 14.04 LTS DockerVersion:1.0.0}

This is the start of the debug page. Still need to add cgroup and namespaces status plus the final debug page.
Maybe not in this PR, but we now have cadvisor/version which has the cAdvisor version. We should display it here too.