Standardize File handling with FsHelpers (#110)

## Summary

* Standardize File handling with FsHelpers
* Better central place to manage to logic of if files exist/open for
reading/writing

lib/Serialization/Serialization.h

@@ -1,4 +1,6 @@
 #pragma once
+#include <FS.h>
+
 #include <iostream>
 
 namespace serialization {
@@ -7,21 +9,44 @@ static void writePod(std::ostream& os, const T& value) {
   os.write(reinterpret_cast<const char*>(&value), sizeof(T));
 }
 
+template <typename T>
+static void writePod(File& file, const T& value) {
+  file.write(reinterpret_cast<const uint8_t*>(&value), sizeof(T));
+}
+
 template <typename T>
 static void readPod(std::istream& is, T& value) {
   is.read(reinterpret_cast<char*>(&value), sizeof(T));
 }
 
+template <typename T>
+static void readPod(File& file, T& value) {
+  file.read(reinterpret_cast<uint8_t*>(&value), sizeof(T));
+}
+
 static void writeString(std::ostream& os, const std::string& s) {
   const uint32_t len = s.size();
   writePod(os, len);
   os.write(s.data(), len);
 }
 
+static void writeString(File& file, const std::string& s) {
+  const uint32_t len = s.size();
+  writePod(file, len);
+  file.write(reinterpret_cast<const uint8_t*>(s.data()), len);
+}
+
 static void readString(std::istream& is, std::string& s) {
   uint32_t len;
   readPod(is, len);
   s.resize(len);
   is.read(&s[0], len);
 }
+
+static void readString(File& file, std::string& s) {
+  uint32_t len;
+  readPod(file, len);
+  s.resize(len);
+  file.read(reinterpret_cast<uint8_t*>(&s[0]), len);
+}
 }  // namespace serialization