Fix of PublishAspNet5Website given by microsoft to support slots

PublishAspNet5Website.ps1

param($websiteName, $packOutput, $slot)
#fix for the script provided here https://msdn.microsoft.com/en-us/Library/vs/alm/Build/azure/deploy-aspnet5?f=255&MSPPError=-2147217396
$website = $null;
$baseUrl = $websiteName;
if($slot -eq $null){
    $website = Get-AzureWebsite -Name $websiteName
 } else {
    $baseUrl += "-" + $slot
    $website = Get-AzureWebsite -Name $websiteName -Slot $slot
 }

# get the scm url to use with MSDeploy.  By default this will be the second in the array
$msdeployurl = $website.EnabledHostNames | ? {$_ -like "*" + $baseUrl + ".scm*" }
$passwordIndex = (([array]::IndexOf($website.EnabledHostNames, $msdeployurl)) + 1) / 2;

$siteProperties = $website.SiteProperties.Properties

$userName = if($website.PublishingUsername -eq $null) {($siteProperties | ?{ $_.Name -eq "PublishingUsername" }).Value | select -first 1 -Skip ($passwordIndex-1)} else {$website.PublishingUsername}
$pw = if($website.PublishingPassword -eq $null) { ($siteProperties | ?{ $_.Name -eq "PublishingPassword" }).Value | select -first 1 -Skip ($passwordIndex-1)} else {$website.PublishingPassword}

$publishProperties = @{'WebPublishMethod'='MSDeploy';
                        'MSDeployServiceUrl'=$msdeployurl;
                        'DeployIisAppPath'=$website.Name;
                        'Username'=$userName;
                        'Password'=$pw}


$publishScript = "${env:ProgramFiles(x86)}\Microsoft Visual Studio 14.0\Common7\IDE\Extensions\Microsoft\Web Tools\Publish\Scripts\default-publish.ps1"


. $publishScript -publishProperties $publishProperties  -packOutput $packOutput

Also submitted a PR to what I believe is the source of the documentation https://github.com/chrisrpatterson/TeamBuildAspNet5Sample/pull/4