Improve tile cache retention when changing GPX track to one which substantially overlaps the previous track
Full rewrite - all features except basic GPX navigation are new - see description.
* Fix critical GPX upload bug
* Add support for large GPX files (extremely large files will be automatically simplified to fit on Pebble)
* Improve support for Time Round and Time 2 devices
* Increase location update rate to 0.5 Hz
* Display alert when waiting for phone connection or GPX data
Display and follow a track, with speed, heading, and time.