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_app.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include "tt_app_manifest.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef void* AppHandle;
+
+/** @return the bundle that belongs to this application, or null if it wasn't started with parameters. */
+BundleHandle _Nullable tt_app_get_parameters(AppHandle handle);
+
+/**
+ * Set the result before closing an app.
+ * The result and bundle are passed along to the app that launched this app, when this app is closed.
+ * @param[in] handle the app context handle to set the result for
+ * @param[in] result the result state to set
+ * @param[in] bundle the result bundle to set
+ */
+void tt_app_set_result(AppHandle handle, Result result, BundleHandle _Nullable bundle);
+
+/** @return true if a result was set for this app context */
+bool tt_app_has_result(AppHandle handle);
+
+/**
+ * Start an app by id.
+ * @param[in] appId the app manifest id
+ */
+void tt_app_start(const char* appId);
+
+/**
+ * Start an app by id and bundle.
+ * @param[in] appId the app manifest id
+* @param[in] parameters the parameters to pass onto the starting app
+ */
+void tt_app_start_with_bundle(const char* appId, BundleHandle parameters);
+
+#ifdef __cplusplus
+}
+#endif