Creates a new BasicSettings class in common/settings, and forces setting
a default and label for each setting that uses it in common/settings.
Moves defaults and labels from both frontends into common settings.
Creates a helper function in each frontend to facillitate reading the
settings now with the new default and label properties.
Settings::Setting is also now a subclass of Settings::BasicSetting. Also
adds documentation for both Setting and BasicSetting.
The function is unused if YUZU_ENABLE_BOXCAT is disabled, causing a
-Wunused-funciton error when compiled.
Wrapping it with `#ifdef YUZU_ENABLE_BOXCAT` to prevent compiling the
function when the variable is disabled. Opting to not use [[maybe
unused]] in case the function is totally unused in the future.
