add rendering routines for devices

gui/include/DeviceRenderer.hpp

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <memory>
+#include <SDL.h>
+#include "Device.hpp"
+
+struct SDL_Renderer;
+
+class DeviceRenderer {
+public:
+    DeviceRenderer(std::shared_ptr<Device> device, uint16_t x, uint16_t y);
+
+    void Render(SDL_Renderer* renderer) const;
+    void Deselect();
+
+private:
+    SDL_FRect bbox;
+    bool selected;
+    std::shared_ptr<Device> device;
+};