Previously the only VM Provider was vSphere however this made testing and making
changes difficult as it required a functioning vSphere instance. This commit
adds a Dummy Provider which presents a VM provider to Pool Manager but manages
provisioned "VM"s in a hashtable. The Dummy Provider can also be configured to
randomly fail operations and take random amounts of time to perform operations,
such as cloning a VM, which is useful to see how the Pool Manager copes with
these events.
This commit also updates the configuration YAML documentation and adds
appropriate unit tests.
