Sim model editor: fix some diode parameters

This fixes a default value (reverse breakdown voltage was 0, should be infinity) and some tempco units in the diode spice model editor. No functional difference, this is just cosmetic/informational.

For reference, see section 7.2 in the ngspice manual: https://ngspice.sourceforge.io/docs/ngspice-manual.pdf

The breakdown voltage issue was pointed out on the forum: https://forum.kicad.info/t/simple-1ph-rectifier-doesnt-compute/42323/2?u=gkeeth

I left the other device types for another day, my eyes got fuzzy. I expect this would cherrypick cleanly onto 7.0 as well, but I haven't tried.