On the content, user categories are defined as service account and
normal user. However regular user is written at one place instead
of normal user. This replaces the regular user with normal user
for the consistency.
The option --authentication-token-webhook-config-file is for specifying
the configuration file which uses the kubeconfig file format, so this
replaces kubeconfig with configuration for avoiding confusions.
The last change is updating the order of 'clusters' and 'users' for
fitting the following example to read easily.
76b7f9cb1a