If people are trying to use the Docker image to check their cluster, there's a
big likelyhood of them hitting the error message saying that either `kubectl`
or `kubelet` need to be found in order for `kube-bench` to be able to determine
the Kubernetes version in use.

This adds a tip that the version can be specified manually with the `--version`
flag which is a lot easier than having to make a new Docker image with the
right version of `kubelet`/`kubectl` in order for `kube-bench` to work.

This change unifies all config files, podspecs and unitfiles under
a single component configuration key; `config`.

improve error messages.

The server version is used to load the correct benchmark check
to run against the Kubernetes cluster.

Reorder YAML to make a bit more sense. Allow for optional components, and a config file that we don’t think exists. 

printlnWarn: prints warning with a newline.
sprintWarn: returns an optionally contextualized warning string.