Keep Through Hole pads on external layers should be ON by default, because
such a pad does not allow soldering/unsoldering, if this option this option is OFF
Also rename dialog_enum_pads.fbp as dialog_enum_pads_base.fbp, as usual
This option removes copper layers from pads and vias where they are not
connected to other board elements. This allows the inner layers to be
more closely routed if the via landing pad is not needed.
Fixes https://gitlab.com/kicad/code/kicad/issues/1835