Add kvminstall.ps1 to allow easier acquisition of KVM

removed kvmsetup.cmd
Updated kvm.cmd and kvm.ps1

This should allow something like: 

```
@powershell -NoProfile -ExecutionPolicy unrestricted -Command "iex ((new-object net.webclient).DownloadString('https://raw.githubusercontent.com/aspnet/Home/master/kvminstall.ps1'))
```