Fix the problem that some menus do not support translation

[Wingdinggaster656]

While players generally don't install just one submod once they start installing them, seriously, has no one in all this time found it jarring to show Submods even when only one is installed?

I found it quite jarring anyway, so I've now made it so that it doesn't appear in plural form when there's only one submod.

Incidentally, I also:

1. Removed some store. that were useless.
2. Added translation support to the Submod menu. I see that _() is used every menu else, so I think that should be an oversight here.

[Booplicate]

I don't see a point in this. It can be more confusing to users, complicates code, possibly messes up with styles (due to different line length). Have you really seen anywhere a label change mod - mods? Should we do that for everything like:
setting - settings
hotkey - hotkeys
alert - alerts
it's weird

[Wingdinggaster656]

On a second thought, I also feel as if it does seem like there's nothing wrong with keeping it as Submods all the time anymore. Yesterday for some reason the more I looked at it the more uncomfortable it became.

Let's just fix the "Submod menu not supporting translation" thing for this PR.

[dreamscached]

While you're at it, consider doing the same to the rest of the use game_menu — they lack translation too.

[Wingdinggaster656]

While you're at it, consider doing the same to the rest of the use game_menu — they lack translation too.

Good idea. Done.