Allow disabling/removing k3s components

[bojanraic]

At the moment, it seems that only components that are considered civo marketplace applications can be removed. k3s includes several other components, such as coredns, servicelb, traefik, local-storage, metrics-server. metrics-server and traefik are already removable, but not others. I can understand if coredns should remain unmodifiable, but I believe local-storage and servicelb should be removable.

I am especially interested in being able to disable local-storage/local-path-provisioner since I will typically install longhorn. If I clean up local-path-provisioner manually and reboot the master node, it comes back (since it is not disabled from k3s point of view) and then I will have two default storage classes (local-path and longhorn) as described in #12.