Integrate w| addon localization system (language packs)

[piqey]

Garry's Mod has a system for addon localization that we should probably set up this project to make use of. Earlier as opposed to later, as by the nature of this system makes it difficult to expand later-on.

At the moment, we can only offer support for English and Danish, but it's as I said before: We want support for this system now instead of later because of how much harder it would and will be to add support to an unsupported system rather than building a supported system from the ground up.