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

src/main.cpp

@@ -160,7 +160,12 @@ void onGoHome() {
 
 void setup() {
   t1 = millis();
-  Serial.begin(115200);
+
+  // Only start serial if USB connected
+  pinMode(UART0_RXD, INPUT);
+  if (digitalRead(UART0_RXD) == HIGH) {
+    Serial.begin(115200);
+  }
 
   Serial.printf("[%lu] [   ] Starting CrossPoint version " CROSSPOINT_VERSION "\n", millis());