Solder layer only PTH footprints

[Bert Timmerman]

Add a mode for creating "solder layer only" footprints for PTH packages.
Basically every pin would consist of a hole (use the "HOLE" flag on a pin) and add a pad on the solder side (use "ONSOLDER" flag here).

Example:

Element["" "CAPPR512____SLO.fp" "C?" "" 97000 208000 8000 -28000 0 100 ""]
(
         Pin[0 0 0 3000 6600 3000 "" "1" "hole,square"]
         Pin[20000 0 0 3000 6600 3000 "" "2" "hole"]
         Pad[0 0 100 0 6000 3000 9000 "" "1" "onsolder,square"]
         Pad[20000 0 20100 0 6000 3000 9000 "" "2" "onsolder,edge2"]
         ElementArc [10000 0 20000 20000 0 360 1000]

         )