put main timing loop on its own thread

added startup "chirp" sound, added documentation for sounds ...

typos

display temperature sentinel at startup

collapse profile switch handling into a single thread, further reorg of supporting functions

consolidate temperature monitoring into a single thread, slight reordering of subroutine definitions

initial set of basic docs complete ...

readme formatting

minor doc cleanup

more doc cleanup, update todo

typo and clarification

clarify/cleanup docs in code and md file for 1-wire support

more cleanup and clarification

update note on 1-wire support, fix typo

reorganize readme and add section on operating the timer

add description of temperature sentinel, tidy up todos

comment typo

add README.md

continuously monitor profile switch allowing user to change it while running, update todos with cleanup tasks

fix display dimming based on profile switch setting at boot and timer start

add logic to read the profile selection switch

parameterize beep() to use different sounds for start/stop and interval alarms

added time/temp spreadsheet to repo, trimmed todos

audible alert on start/stop, simplify beep sound

add support for piezo buzzer beeps

configure temp probe handling to use /opt/devtimer/temp_probe symlink

further cleanup and tuning of footswitch debounce logic

tune footswitch debounce logic

implement foot switch handling as an isr with rudimentary debounce logic

update todo

canonicalize references to wiringpi methods and constants

enable basic footswitch control

update todos

initialize the time display on boot

remove unneeded globals file from repo, update todos

cleanup out of range temperature handling

fix leading zero suppression logic, generally tidy up temperature reporting

give time and temp led device objects more descriptive names

update todos

update todos

suppress leading zeros in temp display, add startup temp sentinel, reorg constants and globals