Basic lib for parsing dataflash logs with js.
Extracted from https://github.com/ArduPilot/UAVLogViewer/blob/master/src/tools/parsers/dataflashParser.js, which hopefully will use it as a module soon.

to test, cd into the directory, `python -m http.server`, then open your browser at http://localhost:8080
press the button and pick a log file. it will be parsed and the output should show in the console.