RTC: pull rtc code into own file for cleanup

src/gps/RTC.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "configuration.h"
+#include "sys/time.h"
+#include <Arduino.h>
+
+extern bool timeSetFromGPS; // We try to set our time from GPS each time we wake from sleep
+
+/// If we haven't yet set our RTC this boot, set it from a GPS derived time
+bool perhapsSetRTC(const struct timeval *tv);
+bool perhapsSetRTC(struct tm &t);
+
+/// Return time since 1970 in secs.  Until we have a GPS lock we will be returning time based at zero
+uint32_t getTime();
+
+/// Return time since 1970 in secs.  If we don't have a GPS lock return zero
+uint32_t getValidTime();
+
+void readFromRTC();