Add the MS FGD and clean it up

[SaintWish]

Since the FGD points to map entities in the code for maps to use probably seems like a good idea to add it to this repo.

We also need to work towards cleaning it up because we have 2 MS FGDs and they're a mess.

[frendship-loost]

msc_fgd_jackeditor.zip

I thought this fgd was part of our game distribution? It is a merged fgd intended for use in JACK editor. I also load zhlt.fgd (included with compiler tools) alongside this fgd linked above.

[SaintWish]

Oh interesting, yeah we don't have that one or I don't at least. That contains all the map entity definitions?

[frendship-loost]

Yeah it had been updated as recently as 2017, check out the changelog the fgd was created by "MS:C Community". I don't know every last detail about our entities by any means, but this is the most organized and updated fgd we have available IMO.

[SaintWish]

Sounds good, I'll commit that one then.