Change: Fix windows bios inventory

Fix inclusion of PSComputername into System manufacturer Add System serial
number and System version support

Ref: https://dev.cfengine.com/issues/6378
@nickanderson - the invocation of powershell in general is usually pretty slow... could the result of a plain `gwmi Win32_ComputerSystem | fl *` be cached rather than invoking multiple times? Same for other WMI lookups?

Note: `| fl *` portion is not necessary but you will return far more details with it.