Nerfed EMP's against augmented limbs

Because there's not much benefit to only having a few limbs augmented,
and 120/60 damage just silly.  For comparison, cyborgs take 20 damage
total from an EMP and 5-10 stun, and humans take 60 brute damage for
being just outside the gibbing range of a bomb.

This PR brings the average damage from a strong EMP to an aug down to
48, and from a weak EMP down to 30.  The stun against a full aug is
still very likely to be around 10 or 5, respectively.  This is on top of
having weapons drained, headsets disabled, etc.

(I don't know what's up with the extra commits in the commit log, but it's not affecting the diff, and I can't re-fork until https://github.com/tgstation/-tg-station/pull/2845 gets merged.)