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/hal/Display.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include "lvgl.h"
+
+namespace tt::hal {
+
+class Touch;
+
+class Display {
+public:
+    virtual bool start() = 0;
+    virtual bool stop() = 0;
+
+    virtual void setPowerOn(bool turnOn) {}
+    virtual bool isPoweredOn() const { return true; }
+    virtual bool supportsPowerControl() const { return false; }
+
+    virtual Touch* _Nullable createTouch() = 0;
+
+    /** Set a value in the range [0, 255] */
+    virtual void setBacklightDuty(uint8_t backlightDuty) { /* NO-OP */ }
+    virtual bool supportsBacklightDuty() const { return false; }
+
+    /** Set a value in the range [0, 255] */
+    virtual void setGammaCurve(uint8_t index) { /* NO-OP */ }
+    virtual uint8_t getGammaCurveCount() const { return 0; };
+
+    /** After start() returns true, this should return a valid pointer until stop() is called and returns true */
+    virtual lv_display_t* _Nullable getLvglDisplay() const = 0;
+};
+
+}