Factor out AppGLFW base class

The intention here is to get rid of scaffolding in the consumer
application class and allow to focus on the "important bits".

src/main.cpp

@@ -1,7 +1,7 @@
 #include <iostream>
 #include <memory>
 
-#include "AppGLFW.hpp"
+#include "MyApp.hpp"
 #include "resources/resource.hpp"
 #include "uiresources.h"
 #include "utilities/ILog.hpp"
@@ -23,7 +23,7 @@ int main(int argc, char** argv)
     logger->ChangeLevel(utils::log::LogLevel::Debug);
     auto image_pool{std::make_unique<resources::ImageResourcePool>()};
 
-    auto app = pixelarium::ui::AppGLFW(logger, image_pool);
+    pixelarium::ui::MyApp app = pixelarium::ui::MyApp(logger, image_pool);
 
-    return app.Run();
+    app.Start();
 }