Instances of the pulsometer state structure are only passed
to the pulsometer itself and only via the opaque context pointer.
No other code uses it. There is no need to expose it in a header file
so make it an implementation detail of the watch face.
Update the copyrights to include full name attribution to all
who contributed to the pulsometer watch face, including myself.
Also add an SPDX license identifier header comment to the files.
Implements an advanced pulsometer that can be recalibrated by the user.
The main clock face now displays the measured pulses per minute.
The day of month digits now display the pulsometer calibration.
The light button now cycles through integer graduations
which now range from 1 to 39 pulses per minute.
Long presses of the light button cycle by 10 instead of 1.
The watch face's responsiveness to input has been carefully optimized.
The code has been reorganized and generally improved.
* Move from .c to .h as needed for consistency.
* When missing from both, copy from pull request or wiki.
* When missing entirely, infer functionality from source code.
