Cleanup for use with unit test

Splash screen is optional. Also remove some unused class definition.

src/ui/MainWindow.cc

@@ -88,7 +88,6 @@ const QString MainWindow::defaultLightStyle = ":files/styles/style-light.css";
 MainWindow* MainWindow::_create(QSplashScreen* splashScreen, enum MainWindow::CUSTOM_MODE mode)
 {
     Q_ASSERT(_instance == NULL);
-    Q_ASSERT(splashScreen);
     
     new MainWindow(splashScreen, mode);
     
@@ -125,12 +124,12 @@ MainWindow::MainWindow(QSplashScreen* splashScreen, enum MainWindow::CUSTOM_MODE
     menuActionHelper(new MenuActionHelper()),
     _splashScreen(splashScreen)
 {
-    Q_ASSERT(splashScreen);
-    
     Q_ASSERT(_instance == NULL);
     _instance = this;
     
-    connect(this, &MainWindow::initStatusChanged, splashScreen, &QSplashScreen::showMessage);
+    if (splashScreen) {
+        connect(this, &MainWindow::initStatusChanged, splashScreen, &QSplashScreen::showMessage);
+    }
     
     this->setAttribute(Qt::WA_DeleteOnClose);
     connect(menuActionHelper, SIGNAL(needToShowDockWidget(QString,bool)),SLOT(showDockWidget(QString,bool)));

src/ui/MainWindow.h

@@ -468,14 +468,9 @@ private slots:
     void _saveTempFlightDataLog(QString tempLogfile);
 
 private:
-    /// Constructor is private since all creation should be through MainWindow::instance.
+    /// Constructor is private since all creation should be through MainWindow::_create
     MainWindow(QSplashScreen* splashScreen, enum MainWindow::CUSTOM_MODE mode);
     
-    /// @brief Two phase construction such that MainWindow::instance is available to code
-    void _init(void);
-    
-    friend class QGCApplication;
-    
     void _hideSplashScreen(void);
     void _openUrl(const QString& url, const QString& errorMessage);