Finalizes Mutantrace Datum Update

https://github.com/tgstation/-tg-station/pull/3609

Squashes the commits from the above pull request. Should hopefully be a
lot less cluttered.
Merge remote-tracking branch 'upstream/master' into mutrace-final
Encapsulates if() statement

Profakos pointed this out
Aaaaaaaaaaaaaaarghhhhh

IN MY DEFENSE, you can't actually be set on fire in the first place if
you have HEATRES or NOFIRE in your specflags, so it was easy for me to
overlook this one.

This is really more of an issue with BYOND than anything else.
Added some of Cheridan's suggestions

*Removed 'Make 2spooky' admin command
*You can still gib even if you don't have DNA
*species_types now uses absolute pathing (probably not gonna do the same
for species.dm, mainly because with such a large file it strikes me as
practical to keep the paths relative)
Merge pull request #3959 from CollenN/mutrace-final

Finalizes Mutantrace Datum Update