Extend to also support remote zfs+nfs PVs

[asteven]

Comparing kubernetes-zfs-provisioner with local-zfs-provisioner it seems that it should be very simple to provide both features in one provisioner.

Plan:

• rename local-zfs-provisioner to zfs-provisioner
• support 2 different kind of storage classes:
  • local zfs provisioning with host affinity (what local-zfs-provisioner does)
  • zfs provisioning on dedicated given host and setup exports via nfs (what kubernetes-zfs-provisioner does)
  • capture all differences/parameters in storage class while defaulting to local-zfs-provisioner
  • param to enable overcommit on/off in storage class (quota vs refquota/reflimit)
• change code to inspect storage class and schedule the dataset create/delete pods on either the given storage host or based on host affinity.