Extract saved timezones into a separate model and lazily load full timezones model
This extracts the model for the saved timezones into its own class.
This way we have a better separation between the parts that only need to know the saved timezones and the parts that need access to all system timezones.
Don't create the full timezones model until needed to speed up startup
Fixes #58 (closed)
Edited by Nicolas Fella