This adds two Helm chart values into the documentation with details
that have come up in several issues.
Additionally, it notes that persistent volumes and their claims need
to be removed manually because of current kubernetes and helm design.
This field was added back into the helm chart, but it was not added
back to the documentation. This adds it, then additionally fixes a
few typos in the same file.
* website: initial Kubernetes section with Helm information
* website: extraConfig for clients
* website: add more helm fields
* website: document extraVolumes
* website: document Consul DNS
* website: fix typos and show example of downward API
