Localisation

Have been working on this in secret, some people already contributed translations. There is some documentation at https://github.com/OpenRA/OpenRA/wiki/Translation but still I might need some guidance here @chrisforbes especially for the OpenRA.FileFormats/Manifest.cs part which is largely spaghetti code. Already tried to use a proper field loader with lists that converted to arrays later on, but threw that away because I can't get it to work.