Allow to use an existing metadata sidecar when dumping media.

DiscImageChef/Options.cs

@@ -305,6 +305,9 @@ namespace DiscImageChef
         [Option('O', "options", Default = null,
             HelpText                    = "Comma separated name=value pairs of options to pass to output image plugin")]
         public string Options { get; set; }
+
+        [Option('x', "cicm-xml", Default = null, HelpText = "Take metadata from existing CICM XML sidecar.")]
+        public string CicmXml { get; set; }
     }
 
     [Verb("device-report", HelpText = "Tests the device capabilities and creates an XML report of them.")]