* added hardware requirements in README.md

* added hardware requirements in README.md

Change-Id: I27d670803bea82a68d5eb0e49d4677f4afdce55f

* update k8s to 1.13.3

* update README as well

- Creates and defaults an ansible variable for every configuration option in the `kubeproxy.config.k8s.io/v1alpha1` type spec
  - Fixes vars that were orphaned by removing non-kubeadm
  - Fixes previously harcoded kubeadm values
- Introduces a `main` directory for role default files per component (requires ansible 2.6.0+)
  - Split out just `kube-proxy.yml` in this first effort
- Removes the kube-proxy server field patch task

We should continue to pull out other components from `main.yml` into their own defaults files as I did here for `defaults/main/kube-proxy.yml`. I hope for and will need others to join me in this refactoring across the project until each component config template has a matching role defaults file, with shared defaults in `kubespray-defaults` or `downloads`

* Upgrade kubernetes to v1.13.0

* Remove all precense of scheduler.alpha.kubernetes.io/critical-pod in templates

* Fix cert dir

* Use kubespray v2.8 as baseline for gitlab

Upstream Changes:

  - ingress-nginx 0.21.0 (https://github.com/kubernetes/ingress-nginx/releases/tag/nginx-0.21.0)

Our Changes:

  - Sync templates with upstream changes
  - Remove --default-backend-service requirement. Use the flag only for custom default backends

Upstream Changes:

-   cert-manager 0.5.2 (https://github.com/jetstack/cert-manager/releases/tag/v0.5.2)

Our Changes:

-   Templates sync with upstream manifests

README contains wrong versions. Let's fix that.

* weave: Upgrade to 2.5.0

Upstream Changes:

-   weave 2.5.0 (https://github.com/weaveworks/weave/releases/tag/v2.5.0)
-   Adds support for Kubernetes `hostPort` mapping
-   Adds support for Kubernetes `ipBlock` NetworkPolicy feature

Our Changes:

-   Templates sync with upstream manifests
-   Remove legacy nodePort fix

* BC for weave < 2.5.0

* Adds support for Multus (multiple interfaces) CNI plugin

Multus is a latin word for "Multi". As the name suggests, it acts as a
Multi plugin in Kubernetes and provides multiple network interface
support in a pod. Multus uses the concept of invoking delegates by
grouping multiple plugins into delegates and invoking them in the
sequential order of the CNI configuration file provided in json format.

* Change CNI version (0.1.0->0.3.1) of Contiv to be compatible with Multus

Upstream Changes:

   - coredns v1.2.5 (https://github.com/coredns/coredns/releases/tag/v1.2.5)

NOTE:

   - Switch image repo to https://hub.docker.com/r/coredns/coredns/ (https://github.com/kubernetes-incubator/kubespray/pull/3595#issuecomment-433962973)

This reverts commit 8ba6b601.

Upstream Changes:

-   ingress-nginx 0.20.0 (https://github.com/kubernetes/ingress-nginx/releases/tag/nginx-0.20.0)

Our Changes:

-   Sync templates with upstream changes

* failed

* version_compare

* succeeded

* skipped

* success

* version_compare becomes version since ansible 2.5

* ansible minimal version updated in doc and spec

* last version_compare

* [jjo] add kube-router support

Fixes cloudnativelabs/kube-router#147.

* add kube-router as another network_plugin choice
* support most used kube-router flags via
  `kube_router_foo` vars as other plugins
* implement replacing kube-proxy (--run-service-proxy=true) via
  `kube_proxy_mode: none`, verified in a _non kubeadm_enabled_
  install, should also work for recent kubeadm releases via
  `skipKubeProxyInstall: true` config

* [jjo] address PR#3339 review from @woopstar

* add busybox image used by kube-router to downloads

* fix busybox download groups key

* rework kubeadm_enabled + kube_router_run_service_proxy

- verify it working ok w/the kubeadm_enabled and
  kube_router_run_service_proxy true or false

- introduce `kube_proxy_remove` fact, to decouple logic
  from kube_proxy_mode (which affects kubeadm configmap
  settings, thus no-good to ab-use it to 'none')

* improve kube-router.md re: kubeadm_enabled and kube_router_run_service_proxy

* address @woopstar latest review

* add inventory/sample/group_vars/k8s-cluster/k8s-net-kube-router.yml

* fix kube_router_run_service_proxy conditional for kube-proxy removal

* fix kube_proxy_remove fact (w/ |bool), add some needed kube-proxy tags on my and existing changes

* update kube-router tolerations for 1.12 compatibility

* add PriorityClass to kube-router DaemonSet

* Specify that the cluster.yml playbook should run as root

This is a possible fix for #3388.
The following examples show the option `-b` too:

https://kubernetes.io/docs/setup/custom-cloud/kubespray/
https://github.com/kubernetes-incubator/kubespray/blob/master/docs/getting-started.md#starting-custom-deployment

* Update invocation to include specific root user

* Update comment text according to suggestions

https://github.com/kubernetes/kubernetes/issues/69214

* Upgrade kubernetes to v1.12.0

Use kubeadm v1alpha3 config

* Upgrade coredns and etcd

* Upgrage docker to 18.06

Internet access is not mandatory as long as the user configures all container image repositories to point to internal container registries, in case of on-premises installation with firewall rules preventing direct Internet access.

Upstream Changes:

-   weave 2.4.1 (https://github.com/weaveworks/weave/releases/tag/v2.4.1)

Our Changes:

-   Templates sync with upstream manifests

Upstream Changes:

-   cert-manager 0.5.0 (https://github.com/jetstack/cert-manager/releases/tag/v0.5.0)

Our Changes:

-   Templates sync with upstream manifests