Comment 49 for bug 579443

I remember, I have missed one thing. Below is the more complete list:

* implement tripstats unit selector
* adjust button sizes as suggested by kizza. Possibly adding a confirmation dialog before resetting the stats.
* add condition to ignore gps fixes that have zero speed, to eliminate bloating the stats by gps error meandering. This may need experimentation.
* add average moving speed and max speed