First iteration of menu cleanup

* Broke up the code into more general functions instead of duplicating code
 * Made stuff const and removed variables no longer used
 * Use defines for menu button values
 * Changed the order or things to avoid forward declarations
 * Use array lookup instead of switch-case on some menu options
 * Adjust menu functionification
 * Cleaned up sensor rendering

NuEVI/numenu.h

@@ -0,0 +1,31 @@
+#ifndef __NUMENU_H
+#define __NUMENU_H
+
+#include <cstdint>
+#include <functional>
+
+#define MAX_DEPTH 16
+
+class Adafruit_SSD1306;
+
+class NuMenu
+{
+public:
+    NuMenu(Adafruit_SSD1306 &gfx);
+
+    bool init();
+    void update(uint16_t buttonState);
+
+    void setEnabled(bool state) { _enabled = state; }
+
+    static void drawMenuItems(const char* title, const char* entries[], int count, int selection, int offset = 0);
+
+private:
+    bool _enabled;
+    // MenuPageState _rootMenu;
+    // MenuPageState _pageStack[MAX_DEPTH];
+
+    Adafruit_SSD1306 &_display;
+};
+
+#endif