kicad: use separated libraries

switch source to gitlab as that's the new upstream source

use wrapper variables for everything but i18n
  add sym and fp templates to template path

update meta to reflect kicad's own language
  set license to AGPLv3, according to the source's LICENSE.README

reduce diff between default and unstable in preparation of merging

on debian gets "no module named 'math'"
  pcbnew 3d viewer is unusable (at least on my T410)