Created Unassigned: Script halts with SP Foundation selected [21690]

Script output:
```
- Script halted!
- The Product ID (PIDKey) is missing or badly formatted.
- Check the value of <PIDKey> in "AutoSPInstallerInput.xml" and try again.
```

Although the comment in XML states there is no PIDKey needed when selecting Foundation the validation is still active..

following code at line 268 in AutoSPInstallerFunctions.ps1 should fix the problem

```
$pidKey = $xmlinput.Configuration.Install.PIDKey
$sku = $xmlinput.Configuration.Install.SKU
# Do a rudimentary check on the presence and format of the product key
if ($sku -ne "Foundation" -and $pidKey -notlike "?????-?????-?????-?????-?????")
```