Patch. Remove unused keys from en.txt

[adrian_broher]

There is also UserStringNop, which wraps translatable literals in c++, that are stored in a variable and translated at a later time. You can ignore UserString most of the time if it has something else than a string literal as a parameter.

[adrian_broher]

The hotkey doesn't create the translation key on the fly anymore, but now holds a description attribute, which contains the translation key. The translation key is passed via the factory method and is wrapped by a UserStringNop call.