Split track should duplicate common point

Currently, if you split a track, say, at point #50, point #49 becomes the end of the first track and point #50 becomes the beginning of track 2.

Unless there is a reason I am not seeing for the current behavior, I think this is a small bug: in fact, in this way you loose a segment of the total track between track 49 and track 50, as if you had never traveled that segment.

I think that point #50 should be duplicated and become both the end of track 1 and the start of track 2.

Note that with this change, the "old" behavior can still be recovered if needed (at the expense of a slightly longer procedure) by splitting the track again at point 49 and intentionally deleting the segment between point 49 and point 50.

The opposite is not true: with the current behavior, there is no way to maintain the completeness of the track.