Use gmod language by default.

[sanny-io]

Helix uses English as its default language, but this is not user friendly for those who have gmod set to use a different one. This PR allows Helix to respect whatever language players have selected for gmod.

However, what I was interested in while making these changes is the importance of ix.config.language. It currently has the highest precedence when choosing which language to consider the default. I couldn't find any references to it other than where it is defined and where the language option is added. Is this a variable that can be removed or given less priority than the players' gmod language without any adverse effects?

I want to add one more thing to this PR, but before moving forward with that, I'd like to know if we can simplify some of this.

[impulsh]

I think the client's gmod language should have the highest priority - servers shouldn't really be setting the client's language anyway, especially since any untranslated phrases now fall back to English so it should be less jarring if the server doesn't have phrases for the client's selected language. You can definitely remove ix.config.language

[ExtReMLapin]

I think using the server's language isn't that bad, it reminds the player where he's playing and what people expect from them.