New chronograph and signal features

Operating instructions for v1.7.0

• Timer/Chrono improvements
  • Timer is now Timer/Chrono, as it can now count up too!
  • Timer can now be set by the second, up to 100 hours; and chrono can count up to 100 hours.
  • Timer has new “runout options,“ which control what it does when it runs out: stop, restart (interval), or start chrono, with long or short signal.
  • Chrono displays hundredths of seconds (when under one hour, or under one minute on 4-tube displays).
    • To enable chrono to be both precise in the short term (given DS3231 doesn't do subseconds) and accurate in the long term (given millis() drifts badly), added calibration wrapper for millis() that applies an offset to correct the drift, continuously adjusted per DS3231 (to within ~±20ms at any given time). checkRTC can now perform certain actions – such as the above offset adjustment – only once per timed trigger, so the actions don't accidentally compound.
  • New controls: Up is start/stop; Down gives a lap time (running chrono), toggles runout option (running timer), or resets to 0 (stopped). Holding Select goes directly into setting the timer, which now prompts for hours/mins, then seconds. Variations apply for rotary control.
  • Timer/chrono now follows leading zero option.
  • Timer interval option is removed, since the runout option now covers this. Frees EEPROM loc 25.
• Signals now have beeper pattern options!
  • Long single, short single, double, triple, quadruple, and cuckoo
  • Signals are now timed per millis() rather than a DS3231 counter so that it can be triggered at any arbitrary time, to support the updated chrono/timer and to indicate patterns while setting.
  • Timer “radio sleep” relay is no longer considered a signal (similar to soft switch) so it can happen independently of signal.
• Various bugfixes.
• Config file updates
  • Increased default timeoutSet to 300 seconds (from 120) to allow time to set the timer to the full 100 hours.