The k8s external-dns project now uses the official Kubernetes projects
container registry at k8s.gcr.io. Update all references to use the new
registry.

* Update apiVersions in docs

Update docs to reflect new apiVersions for ingresses and deployments.

* Add selector to apps/v1 deployments

* intial removal of inappropriate terminology
Signed-off-by: Raffaele Di Fazio <raffo@github.com>

* removed other occurrences
Signed-off-by: Raffaele Di Fazio <raffo@github.com>

* gofmt
Signed-off-by: Raffaele Di Fazio <raffo@github.com>

* addresses comment
Signed-off-by: Raffaele Di Fazio <raffo@github.com>

* gofmt
Signed-off-by: Raffaele Di Fazio <raffo@github.com>

Make the DNS service IP consistent with `my-coredns-coredns` in example

There is no coredns tutorial for externalDNS. This pull request makes
coredns based on minikube for working with externalDNS.