Add more language support

* Optional Low-Pass Filtering to suppress high frequency interfering sounds.
* Optional signal rectification to transform high frequency percussive bursts into low frequencies that were otherwise too low to be detected by the microphone.
* Older unreliable modes of operation were removed (auto ranging and tracking) in favor of the more reliable Hint Band mode.
* Built-in help is greatly expanded.

Fixed a problem with Settings visibility when Dark Mode is used in iOS 13.

* Improved signal analysis calculations, making envelope detection unnecessary.
* Use of speaker in "Match RPM sound" mode is louder.
* Revised time-stamp in logging to reflect time of day.
* Configurable logging interval.
* Improved help files.

1. Sample times up to 3 seconds for measuring lower RPM.
2. Envelope detection option.
3. Sound-generating option for manually matching to the engine sound.
4. More extensive help files for each setting option.

iOS 9 compatibility issue fixed.
Added user-configurable sample lengths for faster-changing RPM.
Improved analysis algorithms for better sensitivity and noise rejection.
Added a logging function for saving RPM readings over time and sending them by e-mail.

Fixed a crash in iOS 7 devices.

Improved analysis of the engine sound, using an autocorrelation algorithm that provides more reliable RPM readings.
Addition of an automatic mode option; no adjustments needed.
Compatibility with iPhone 5 (software utilizes all of the 4-inch screen).

Spectrum analysis has been improved to better identify the harmonics of the engine sound.

A new Tracking mode has been added to track changing RPM over the entire 500-90,000 RPM range.

The range of harmonics used in analysis is now selectable, using harmonics 1-16.

The 4-cycle, 1-cylinder engine has been added to the list of stock engine configurations.

Detection of a missing microphone for the iPod Touch has been added.