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

TactilityC/Source/tt_app.cpp

@@ -27,4 +27,8 @@ void tt_app_start_with_bundle(const char* appId, BundleHandle parameters) {
     tt::app::start(appId, std::shared_ptr<tt::Bundle>((tt::Bundle*)parameters));
 }
 
+void tt_app_stop() {
+    tt::app::stop();
+}
+
 }