Join-Path prompts for path #Critical

Join-Path needs to be switched over to use command wrapping - see https://www.petri.com/making-powershell-command.

Currently, Join-Path frequently prompts for Path which is very bad since Join-Path is used so frequently.  The predominant problem is caused when named parameters (such as -Path or -ChildPath) are used.

See Fix/Join-Path branch for failing tests.