Added over-voltage alarm.

Added over-voltage alarm, including commands to set the alarm level,
and alarm format. Fixed ADC configuration to obtain full range.
Replaced Morse.ino with didah.ino to fix a build error. Miscellaneous
cleanups.
Fixed over-voltage alarm. Improved documentation. Fixed some mistakes in prompts. Improved response to buttons while transmitting.
Increased frequency of voltage status updates. Improved alarm LED behavior. Fixed Morse erase character (SS prosign). Fixed UI incorrect maximum voltage.
Implemented uptime tracking.
Schematic
Added URL. Created PDF from schematic.
Added pictures, schematic, and BOM.