/tg/ input stripping.

Borrows /tg/ html stripping code.
Ghosts are the first to be given this boon, they now have to deliberately emote things like "Spooky man and it#36&;s friends type crap".
Merge remote-tracking branch 'upstream/dev' into Stripping

Conflicts:
	code/modules/mob/living/carbon/human/whisper.dm
Merge pull request #7104 from PsiOmegaDelta/Stripping

/tg/ input stripping.