Rewrite bearing and distance calculations to use UTM zones

This technique produces reliable bearings although does require you to
specify the UTM zone.
Consider all tracks, even those with manual entry

Simply editing a track to say add a route, causes all the entries to be
marked as 'manual' it seems. Completely manual tracks will have an
evenly spread speed, so as a result their speed anomoly will be 0, and
thus vanish from the binning.
Fix binning for x/y correctness

Grid now matches what I would expect, tracing out my usual cycling
routes through Melbourne.