Compare to other hostpath provisioners and document findings

It would be good to compare and document how our local-storage provisioner relates to others, i.e.

• https://github.com/rancher/local-path-provisioner

Unmaintained:

• https://github.com/torchbox/k8s-hostpath-provisioner

Not supporting dynamic provisioning:

• https://github.com/kubernetes-sigs/sig-storage-local-static-provisioner