* add initial MetalLB docs
* metallb allow disabling the deployment of the metallb speaker
* calico>=3.18 allow using calico to advertise service loadbalancer IPs
* Document the use of MetalLB and Calico
* clean MetalLB docs
* add nodeselector and tolerations for metallb
* remove unnecessary commented lines in metallb template
* set default speaker toleration to match original manifest
* Make metallb image repos configurable
* Moved metallb image repo definitions to download role defaults
* Removed comment. These are set in download defaults
This changes MetalLB contrib to one of addons for deploying MetalLB with
Kubernetes cluster deployment. By the default, Kubespray doesn't deploy
MetalLB addon.
