add feature to core2chip to allow more external/internal power/ground pins p_(vss/vdd)(i/e)ck_(0/1/2....)

f

chip dictionary: chip.n_extpower and chip.n_intpower allow addition of more external (p_vsseck_1/2/3, pvddeck_1/2/3) chip power pads and internal chip power pads respectively

the pads must still be added to chip.north/south/east/west and must still not be added to pads.instances