Refactor app access (#205)

- Use `tt::app::` functions to start/stop apps and get current app(context) instead of using loader everywhere
- Removed `tt_service_loader.*` from TactilityC
- Created `tt_app_stop()` for TactilityC
- Bumped version to 0.3.0 to prepare for upcoming release

Tactility/Source/service/screenshot/ScreenshotTask.cpp

@@ -87,7 +87,7 @@ void ScreenshotTask::taskMain() {
                 }
             }
         } else if (work.type == TASK_WORK_TYPE_APPS) {
-            auto appContext = loader::getCurrentAppContext();
+            auto appContext = app::getCurrentAppContext();
             if (appContext != nullptr) {
                 const app::AppManifest& manifest = appContext->getManifest();
                 if (manifest.id != last_app_id) {