[Feature] Allow neutral pronouns for players' characters

[kyle2143]

Noah Buttes asked me to make this last week, so here it is. The main bit is, if you have the neutral pronouns selected (They/Them) then the common pronoun selector procs will use the english neutral pronouns for writing text to the world. ex. examining a character.

gif, bad quality, but w/e.


Technical notes:

- Just adds a boolean var to the appearanceHolder datum called "pronouns". 0 for gendered pronouns, 1 for neutral. I wasn't going for extensiblity, mostly because I have no idea what sorts of things should be extensible from this sort of thing.

- Makes changes to the him_her, he_she, etc. procs in code/procs/mob_procs.dm to check for an appearanceHolder. Really the simplest way I thought to do it.

- this PR has that Robots.dm 512.1453 compatibility thing cherry-picked into it. Sue me.


https://github.com/goonstation/goonstation-2016/pull/94

[Gannets]

We really need to make that menu not suck sometime. Good patch.

[Noah Buttes]

This patch gets the official buttes stamp of approval