#6 enhancement: track route line, not just current position

[Alexey Roytman]

It's very handy to be able to start/stop route tracking on the map, both from NMEA log file or GPS itself.
It can be an option to do one of the following:
- start (if not started) -- this should start drawing route
- stop (if started) -- this should stop adding points to the current route, the route is drawn and not changed
- reset&stop -- route is removed