Language message overhaul, part 1.

Clean up the names of messages. Mark those that are unused as such in code comments. Raise the CPU level while loading a message file, because it really does take half a second to load a 16 KB file on the lowest frequency (what the eff?).
Language file overhaul, part 2. Remove unused messages in all languages.

It's actually reloading icons that takes so much time.