$env:USERNAME can have invalid characters in it for a URI

[elmalakai]

Using the Username to generate the URI for the AD Application can result in an error. I had to do some basic cleaning on it:

$userName = $env:USERNAME
$userName = $userName -replace "[' ]"

I'm sure there is a better way to clean the string for the URI. In the end I added a new param to ask for the App Name.

Also the SecureString issue mentioned above. I didn't change the Input, but added this:

$securePassword = ConvertTo-SecureString $password -AsPlainText -Force
$azureAdApplication = New-AzureRmADApplication -DisplayName $displayName -HomePage $homePage -IdentifierUris $identifierUri -Password $securePassword -Verbose