- Split the actual loading of translations into classes
to encapsulate the loading logic,
- Build a collection of classes to do the different kinds
of translation loading,
- Build a generic function to load something and update a
static pointer to the translation.
This makes installTranslator() much easier to read, and encapsulates
the type-specific loading somewhere else. While here, add a timezone-
translations loader so that the split-out TZ translations also work.
- sometimes a slot is easier than a lambda. Introduce
a macro CALAMARES_RETRANSLATE_SLOT that calls a given
slot in an object on language change.
- extend the retranslator with support for calling slots:
- use Qt's signal/slot mechanism alongside the private
list of functions to call
- provide convenience for obtaining the retranslator of
an object.
In order to avoid deep copies, Qt containers over which we iterate must be const
The remaining unported cases require qAsConst (Qt 5.7) or std::as_const (C++17)
