DRC is not yet smart enough to distinguish jumpered pads when they
touch, so we work around this for 5.1 by using graphical polygons on the
F.Cu layer.
In KiCad 4 there were no polygon pads which resulted in some overlapping
pad constructs. This is no longer required, as well as the old system
causes some nasty problems like duplication of pin numbers and
unconnected warnings. This PR solves the issue for the jumpers by
converting the pads to custom shaped pads as appropriate.
