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/app/i2cscanner/I2cScanner.cpp

@@ -72,7 +72,7 @@ public:
 
 /** Returns the app data if the app is active. Note that this could clash if the same app is started twice and a background thread is slow. */
 std::shared_ptr<I2cScannerApp> _Nullable optApp() {
-    auto appContext = service::loader::getCurrentAppContext();
+    auto appContext = getCurrentAppContext();
     if (appContext != nullptr && appContext->getManifest().id == manifest.id) {
         return std::static_pointer_cast<I2cScannerApp>(appContext->getApp());
     } else {