- Declaring namespace A::B is a C++17 extension, and Calamares
is C++14. Split the namespace declarations.
- While here, fix extra const warning as well.
- Which translations are available is a global property
of Calamares itself, not of the plugins, so getting
the model of available translations should live there.
Move the relevant code (which is simple) from the
Welcome module.
- Use namespace CalamaresUtils::Locale consistently for this service.
- Move locale-related non-GUI support code from the Welcome module
to libcalamares; these are generally useful. Both Label (naming a locale)
and LabelModel (managing a bunch of those Labels) have been moved.
