Zpool module

Create and modify a Zpool.

This Pull Request is based on ansible/ansible#8205. I think it was lost when the Module Repos were reorganized.
I fixed some Errors and add a new Feature: Add new devices to an existing pool. This allows Pools with nested Raid Levels like Raid10 or Raid50. 
Is the plan to document and add flags for every feature potentially used by zfs, or just the features supported by all platforms, or just the ones people use? If it were possible to provide generic feature support that would be much better.