Simplify app registration with TactilityCpp (#7)

- Simplified app registration with a C++ wrapper for the TactilityC.
- Rename the various app classes from `Application` to more specific names like `Calculator` etc.

Apps/GPIO/main/Source/Gpio.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <TactilityCpp/App.h>
+
+#include <tt_app.h>
+#include <tt_mutex.h>
+#include <tt_timer.h>
+
+#include <lvgl.h>
+#include <vector>
+
+class Gpio final : public App {
+
+    std::vector<lv_obj_t*> pinWidgets;
+    std::vector<bool> pinStates;
+    TimerHandle timer;
+    MutexHandle mutex;
+
+    static lv_obj_t* createGpioRowWrapper(lv_obj_t* parent);
+    static void onTimer(void* parameter);
+
+public:
+
+    void onCreate(AppHandle app) override;
+    void onDestroy(AppHandle app) override;
+    void onShow(AppHandle context, lv_obj_t* parent) override;
+    void onHide(AppHandle context) override;
+
+    void startTask();
+    void stopTask();
+
+    void updatePinStates();
+    void updatePinWidgets();
+};