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/Preferences.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+namespace tt {
+
+/**
+ * Settings that persist on NVS flash for ESP32.
+ * On simulator, the settings are only in-memory.
+ */
+class Preferences {
+private:
+    const char* namespace_;
+
+public:
+    explicit Preferences(const char* namespace_) {
+        this->namespace_ = namespace_;
+    }
+
+    bool hasBool(const std::string& key) const;
+    bool hasInt32(const std::string& key) const;
+    bool hasString(const std::string& key) const;
+
+    bool optBool(const std::string& key, bool& out) const;
+    bool optInt32(const std::string& key, int32_t& out) const;
+    bool optString(const std::string& key, std::string& out) const;
+
+    void putBool(const std::string& key, bool value);
+    void putInt32(const std::string& key, int32_t value);
+    void putString(const std::string& key, const std::string& value);
+};
+
+} // namespace