Project restructuring (fixes macOS builds) (#198)

- Create `Include/` folder for all main projects
- Fix some issues here and there (found while moving things)
- All includes are now in `Tactility/` subfolder and must be included with that prefix. This fixes issues with clashing POSIX headers (e.g. `<semaphore.h>` versus Tactility's `Semaphore.h`)

TactilityC/Include/tt_service_loader.h

@@ -0,0 +1,33 @@
+#pragma once
+
+#include "tt_app.h"
+#include "tt_bundle.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Start an application providing a manifest id and an optional bundle.
+ * Execution is always deferred.
+ * This function generally returns immediately unless the scheduler is blocked.
+ * @param[in] id application manifest id
+ * @param[in] bundle an allocated bundle (or NULL) of which the memory ownership is handed over to this function
+ */
+void tt_service_loader_start_app(const char* id, BundleHandle _Nullable bundle);
+
+/**
+ * Stop the currently active app.
+ * Execution is always deferred.
+ * This function generally returns immediately unless the scheduler is blocked.
+ */
+void tt_service_loader_stop_app();
+
+/**
+ * Get the context handle of the app that is currently shown on the screen.
+ */
+AppHandle tt_service_loader_get_current_app();
+
+#ifdef __cplusplus
+}
+#endif