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_selectiondialog.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include "tt_bundle.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Start an app that displays a list of items and allows the user to select one.
+ * @param[in] title the title to show in the toolbar
+ * @param[in] argc the amount of items that the list contains
+ * @param[in] argv the labels of the items in the list
+ */
+void tt_app_selectiondialog_start(const char* title, int argc, const char* argv[]);
+
+/** @return the index of the item that was clicked by the user, or -1 when the user didn't select anything */
+int32_t tt_app_selectiondialog_get_result_index(BundleHandle handle);
+
+#ifdef __cplusplus
+}
+#endif