manoelcampos/cloudsim-plus: Simplifies the way to use PowerModel

The PowerSupply was just delegating everything to PowerModel. After refactoring the latter one to provide a better class hierarchy, remove code duplication and fix bugs (#127), PowerSupply was merged into the PowerModel and the former removed. Now, the way to use PowerModel is as before the release 2.0.0, but with all the benefits of using regular classes to implement power-aware simulations, namely DatacenterSimple, HostSimple and VmSimple. You just need to call Host's setPowerModel(PowerModel powerModel) method to enable power-aware simulations