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`)

TactilityHeadless/Include/Tactility/kernel/SystemEvents.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <cstdint>
+
+namespace tt::kernel {
+
+enum class SystemEvent {
+    BootInitHalBegin,
+    BootInitHalEnd,
+    BootInitI2cBegin,
+    BootInitI2cEnd,
+    BootInitLvglBegin,
+    BootInitLvglEnd,
+    BootSplash,
+    /** Gained IP address */
+    NetworkConnected,
+    NetworkDisconnected,
+    /** An important system time-related event, such as NTP update or time-zone change */
+    Time,
+};
+
+/** Value 0 mean "no subscription" */
+typedef uint32_t SystemEventSubscription;
+
+typedef void (*OnSystemEvent)(SystemEvent event);
+
+void systemEventPublish(SystemEvent event);
+SystemEventSubscription systemEventAddListener(SystemEvent event, OnSystemEvent handler);
+void systemEventRemoveListener(SystemEventSubscription subscription);
+
+}