devtimer / TODO
- Cleanups:

  - Collect globals into a more coherent centralized namespace
  - Cleanup debug handling using that centralized state info
  - Cleanup timer run code into separate thread that gets started/stopped instead of always running with 0 displayed

- Pull globals into a single coherent namespace
- Autodetect temp probe device
- Generate compensation tables at startup based on low/hi range - perhaps limited by times <400ms
- Add code repo to comments header
- Speed up boot time by removing all unneeded boot activity
- Write docs:

     - Startup sentinel
     - Need to symlink /opt/devtimer/temp_probe to actual probe device