Fix elevated global commands

Currently, when elevating kvm.ps1 to to an admin instance of powershell, the commands will run to completion and then close the powershell window before the user can see the result of the command.

This PR adds a -wait option to powershell to wait for keypress after the command is run, and uses this option in the elevated powershell window.

Additionally, Kvm-Global-Upgade wall calling Kvm-Global-Use only when elevated, in addition to already calling Kvm-Use as part of the kvm global install command in the elevated powershell instance (which has been fixed to call kvm-global-use).