Settings Screen and first 2 settings (#18)

* white sleep screen

* quicker pwr button

* no extra spacing between paragraphs

* Added settings class with de/serialization and whiteSleepScreen setting to control inverting the sleep screen

* Added Settings screen for real, made settings a global singleton

* Added setting for extra paragraph spacing.

* fixed typo

* Rework after feedback

* Fixed type from bool to uint8

src/CrossPointSettings.cpp

@@ -0,0 +1,65 @@
+#include "CrossPointSettings.h"
+
+#include <HardwareSerial.h>
+#include <SD.h>
+#include <Serialization.h>
+
+#include <cstdint>
+#include <fstream>
+
+// Initialize the static instance
+CrossPointSettings CrossPointSettings::instance;
+
+constexpr uint8_t SETTINGS_FILE_VERSION = 1;
+constexpr uint8_t SETTINGS_COUNT = 2;
+constexpr char SETTINGS_FILE[] = "/sd/.crosspoint/settings.bin";
+
+bool CrossPointSettings::saveToFile() const {
+  // Make sure the directory exists
+  SD.mkdir("/.crosspoint");
+
+  std::ofstream outputFile(SETTINGS_FILE);
+  serialization::writePod(outputFile, SETTINGS_FILE_VERSION);
+  serialization::writePod(outputFile, SETTINGS_COUNT);
+  serialization::writePod(outputFile, whiteSleepScreen);
+  serialization::writePod(outputFile, extraParagraphSpacing);
+  outputFile.close();
+
+  Serial.printf("[%lu] [CPS] Settings saved to file\n", millis());
+  return true;
+}
+
+bool CrossPointSettings::loadFromFile() {
+  if (!SD.exists(SETTINGS_FILE + 3)) {  // +3 to skip "/sd" prefix
+    Serial.printf("[%lu] [CPS] Settings file does not exist, using defaults\n", millis());
+    return false;
+  }
+
+  std::ifstream inputFile(SETTINGS_FILE);
+
+  uint8_t version;
+  serialization::readPod(inputFile, version);
+  if (version != SETTINGS_FILE_VERSION) {
+    Serial.printf("[%lu] [CPS] Deserialization failed: Unknown version %u\n", millis(), version);
+    inputFile.close();
+    return false;
+  }
+
+  uint8_t fileSettingsCount = 0;
+  serialization::readPod(inputFile, fileSettingsCount);
+
+  // load settings that exist
+  switch (fileSettingsCount) {
+      case 1:
+          serialization::readPod(inputFile, whiteSleepScreen);
+          break;
+      case 2:
+          serialization::readPod(inputFile, whiteSleepScreen);
+          serialization::readPod(inputFile, extraParagraphSpacing);
+          break;
+  }
+
+  inputFile.close();
+  Serial.printf("[%lu] [CPS] Settings loaded from file\n", millis());
+  return true;
+}