Add instrumentation to loop() to capture frame timing acuracy

[nerdoug]

implement gathering metrics on accurately the frame processing is occurring at 20 msec intervals. This may uncover the need to optimize or restructure our code, or to use FREERTOS to get pre-emptive multitasking.

[theAgingApprentice]

We still like the idea of being able to do this but we are not aware of any issue that this may be causing. We will keep this as a low priority item.