Follow-up after the KIBIS and KIBIS GUI merge requests.
- Move KIBIS from Pcbnew to Eeschema space,
- Make KIBIS obtain the Ku/Kd coefficients via the `SPICE_SIMULATOR` class instead of calling the `ngspice` executable via `system()`,
- Allow to toggle between differential and single-ended model in the GUI,
- Various GUI fixes and improvements.
Found via `codespell -q 3 -S *.po,./thirdparty,./Documentation/changelogs -L aactual,acount,aline,alocation,alog,anormal,anumber,aother,apoints,aparent,aray,ba,busses,dout,einstance,leaded,modul,ontext,ot,overide,serie,te,,tesselate,tesselator,tht`