Add a -T option that sets window title.

`cool-retro-term -T myretrosession` sets window name to 'myretrosession'

This is useful especially for people who rely on wmctrl to change windows, now I
can do `wmctrl -a myretrocession` to focus on cool-retro-term.

-T was chosen since it matches classic xterm(1) and other terminal emulators

app/qml/ApplicationSettings.qml

@@ -41,6 +41,8 @@ QtObject{
     property bool fullscreen: false
     property bool showMenubar: true
 
+    property string wintitle: "cool-retro-term"
+
     property real windowOpacity: 1.0
     property real ambientLight: 0.2
     property real contrast: 0.85
@@ -480,6 +482,10 @@ QtObject{
             showMenubar = false;
         }
 
+        if (args.indexOf("-T") !== -1) {
+            wintitle = args[args.indexOf("-T") + 1]
+        }
+
         initializedSettings();
     }
     Component.onDestruction: {