Minor usability fixes

[fperrin]

Hi Tim,

As mentioned by email, a few small tweaks --they're individual commits, so I can split them into small PR if you don't want one or the other.

To clarify "duplicate point before converting it to waypoint": I mostly use GpsPrune for tracks I created myself (either planning or recording). When adding a name to a point, I would see the point be removed from the track, and the track who jump to skip the waypoint. I understand that's how GPX works, that "waypoints" and "trackpoints" are different objects and a waypoint doesn't need to be included in the track, but as a user that was annoying. As said it's a commit on its own, so I can carve it out of that PR if you want.