* Update links to outdated user-guide and admin docs
* Add script for updating outdated links.
* Update regex to include init-containers file.
* Pull upstream, rewrite links in and to namespaces walkthrough.
A newline between `[]` and `()` caused markdown rendering issues when parsed with `kramdown` (Jekyll's markdown parser) strangely enough this was not present on github.com but only on kubernetes.io.
This change moves the newline between _in_ and `rkt.go` to preserve the line length somewhat.