Add support to create X509 certificates based on .crt/.cert

Thanks to @crited

lib/web/ConvertTo-IcingaX509Certificate.psm1

@@ -0,0 +1,48 @@
+function ConvertTo-IcingaX509Certificate()
+{
+    param(
+        [string]$CertFile          = $null,
+        [string]$OutFile           = $null,
+        [switch]$Force             = $FALSE
+    );
+
+    # Use an empty password for converted certificates
+    $Password       = $null;
+    # Use a target file to specify if we use temp files or not
+    $TargetFile     = $null;
+    # Temp Cert
+    [bool]$TempFile = $FALSE;
+
+    # Create a temp file to store the certificate in
+    if ([string]::IsNullOrEmpty($OutFile)) {
+        # Create a temporary file for full path and name
+        $TargetFile = New-IcingaTemporaryFile;
+        # Get the actual path to work with
+        $TargetFile = $TargetFile.FullName;
+        # Set internally that we are using a temp file
+        $TempFile   = $TRUE;
+        # Delete the file again
+        Remove-Item $TargetFile -Force -ErrorAction SilentlyContinue;
+    }
+
+    # Convert our certificate if our target file does not exist
+    # it is a temp file or we force its creation
+    if (-Not (Test-Path $TargetFile) -Or $TempFile -Or $Force) {
+        Write-Output "$Password
+        $Password" | certutil -mergepfx "$CertFile" "$TargetFile" | Out-Null;
+    }
+
+    # If no target file exists afterwards (a valid PFX certificate)
+    # then throw an exception
+    if (-Not (Test-Path $TargetFile)) {
+        throw 'The specified/created certificate file could not be found.';
+    }
+
+    # Now load the actual certificate from the path
+    $Certificate = New-Object Security.Cryptography.X509Certificates.X509Certificate2 $TargetFile;
+    # Delete the PFX-Certificate which will be present after certutil merge
+    Remove-Item $TargetFile -Force -ErrorAction SilentlyContinue;
+
+    # Return the certificate
+    return $Certificate
+}