Correctly handle public Azure Blob Storage containers containing one file

[petergs]

This PR (1) correctly handles single-file public containers for Azure Blob Storage and (2) updates input file line counting logic to correctly handle empty lines at the end of the file (permutations.txt).

For (1), the current script will print Empty Public Container Available: for a public Azure Blob Storage container with a single file. The fix wraps the XML response in an array to ensure that $foundUrl is a single-element Object[] rather than a single XmlElement (whose .Length property would be $null) when there is only one file in the container.

For (2), calls to Write-Progress will error when there are empty lines anywhere in $Permutations or $Folders as the words iterator will exceed the line count calculation. This results in a value >100 getting passed to the -PercentComplete parameter.