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/service/Service.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <memory>
+
+namespace tt::service {
+
+// Forward declaration
+class ServiceContext;
+
+class Service {
+
+public:
+
+    Service() = default;
+    virtual ~Service() = default;
+
+    virtual void onStart(ServiceContext& serviceContext) {}
+    virtual void onStop(ServiceContext& serviceContext) {}
+};
+
+template<typename T>
+std::shared_ptr<Service> create() { return std::shared_ptr<T>(new T); }
+
+}