Until now, 2 tracks were seen as connected only if one end of the first track is *exactly* on one end of the other track.
Now the 2 ends are seen as connected when they are "near" i.e. the distance between the 2 ends is < track width/2
and therefore tracks are now dragged when a end point is inside a pad, not necessary on the pad position.
However, drag functions still need more cleanup.
therefore tracks which have a end point inside a pad, but not necessaryexactly to the pad position are seen as connected, and are no more removed.
Side effect: reconnect to pads option is removed, because it is useless.
TODO: use this algorithm in drag functions.
Minor other fixes
jean-pierre charras