Update the Windows install.

windows/resources/install-7zip.ps1

@@ -0,0 +1,12 @@
+. .\resources\get-file.ps1
+if (-not (Test-Path "c:\Program Files\7-Zip\7z.exe")) {
+	$cpu = $env:PROCESSOR_ARCHITECTURE
+	Write-Host "Downloading and Installing 7-Zip for $cpu" -ForegroundColor Cyan
+	if ($cpu -eq "x86") {
+		$zip7 = Get-File http://www.7-zip.org/a/7z1604.msi
+	}
+	else {
+		$zip7 = Get-File http://www.7-zip.org/a/7z1604-x64.msi
+	}
+	Start-Process msiexec "/i $zip7 /passive /qb" -Wait
+}