Launcher: allow different texts for Fly! button

Requested by Michael Danilov for Russian translation

src/GUI/LauncherController.cxx

@@ -891,6 +891,19 @@ QUrl LauncherController::flyIconUrl() const
     return QUrl{"qrc:///svg/toolbox-fly"};
 }
 
+QString LauncherController::flyButtonLabel() const
+{
+    if (m_aircraftType == Helicopter) {
+        return tr("Fly!", "For a helicopter");
+    } else if (m_selectedAircraftInfo) {
+        if (m_selectedAircraftInfo->hasTag("spaceship")) {
+            return tr("Fly!", "For a spaceship");
+        }
+    }
+
+    return tr("Fly!");
+}
+
 QUrl LauncherController::urlToDataPath(QString relPath) const
 {
     QString absFilePath = QString::fromStdString(globals->get_fg_root().utf8Str());

src/GUI/LauncherController.hxx

@@ -87,6 +87,7 @@ class LauncherController : public QObject
 	Q_PROPERTY(QSize minimumWindowSize READ minWindowSize WRITE setMinWindowSize NOTIFY minWindowSizeChanged)
 
     Q_PROPERTY(QUrl flyIconUrl READ flyIconUrl NOTIFY selectedAircraftChanged)
+    Q_PROPERTY(QUrl flyButtonLabel READ flyButtonLabel NOTIFY selectedAircraftChanged)
 
     Q_PROPERTY(bool inAppMode READ inApp NOTIFY inAppChanged)
 
@@ -224,6 +225,7 @@ public:
         return m_versionLaunchCount;
     }
 
+    QString flyButtonLabel() const;
 signals:
 
     void selectedAircraftChanged(QUrl selectedAircraft);

src/GUI/qml/Sidebar.qml

@@ -70,7 +70,7 @@ Rectangle {
 
     SidebarButton {
         id: flyButton
-        label: qsTr("Fly!")
+        label: _launcher.flyButtonLabel
         anchors.bottom: parent.bottom
         enabled: _launcher.canFly
         disabledText: qsTr("The selected aircraft is not installed or has updates pending")