[openstack|compute] Basic examples for Compute

This contains some basics examples on how to set up a VM, do power
operations, and find floating IP pools. It should be enough for a
beginner to get started and familiar with Fog so that more complex
things can be searched by the user.

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Merge pull request #2359 from eLobato/openstack_compute_example

[openstack|compute] Basic examples for Compute