winrt: Add more Powershell logging to RT install

winrt: Add more Powershell logging to RT install

RT install Powershell script was using echo.  Now use transcript
recording (which will also include OS, Powershell version, and other
info).  Also, use Write-Host, Write-Warning, and Write-Error to
make errors and warnings more obvious.

NOTE: This includes intentional debug code enablement so I can
retrieve an RT install that does not remove a copy of the
Powershell log file.  This will be fixed quickly after the RT install
is generated on CruiseControl.