Create the support for Parallels in OpenNebula

In case we build on a macOS host, we want to use Parallels to launch the VM on a macOS host. This requires a mechanism to actually control Parallels.

The easiest way might be that we still let OpenNebula create a deployment.0 -file (XML format), but the deploy hooks don't launch virsh and let virsh create a domain using this XML file, but instead we hijack the commands and run parallels instead. We also have to convert the monitoring systems etc to accommodate.

The macOS hosts are thrown into their own Cluster in OpenNebula. That way we can control which hosts macOS builds are going to be built on top of.