Errors when loading translations

[matty0ung]

We currently have void Localization::loadTranslations() Error loading translations logged on many occasions. I think it's because we're not ensuring the Qt built-in translations are present. There are also some improvements we could make to the code that switches languages to make it a bit more robust.

Need to check also that the program correctly picks up the localised decimal separator when you override the default language, eg "1.070 sg" in the UK = "1,070 sg" in France.

(There is a separate issue that you need to close and reopen the program after you change language in order for everything to get updated. We'll hold off trying to fix that for now as it's quite a bit of work and most people don't change the language very often.)

[matty0ung]

Fixed in 4.0.11.