BROKEN / INTERMEDIATE. Dilpad.pm moved to Generator.pm. This is an intermediate change to help prevent issues with putting a new file into Dilpad.pm in the same commit.
* GEDA::PCB::Footprint::Generator carved away from GEDA::PCB::Footprint::Dilpad and made into its base class.
* GEDA::PCB::Footprint::Twopad adapted from 2pad.cgi, and also derived from GEDA::PCB::Footprint::Generator.
* 2pad.pl is analogous (and almost identical) to dilpad.pl.