Added ability to unmount the usb thumbdrive / gps at the end of the run.
rearranged reading of the config file and setting up logging.
Two intertwined changes not worth separating out.

1. Move a big block outside of a try/except/else clause and just run the else part if the exception didn't return.

2. Added progress saving so that we don't process tracks that have been processed a dozen times before.