Refactoring QucsSettings

[iwbnwif]

Currently there is a structure tQucsSettings which has one instance QucsSettings that holds a copy of [most] of the application settings.

To some extent, this duplicates the functionality of QSettings which is designed to provide easy access to all application settings.

I would like to propose replacing QucsSettings with the direct use of QSettings via a static singleton access point.

So, to access the Qucsator binary, you would call _settings::Get().item<QString>("Qucsator"); instead of QucsSettings.Qucsator.

In this case ::item() would return either the stored key for "Qucsator" or the default value if one is defined.

The default values would be stored in a std::map.

Whilst this may look slightly more unwieldy, I think it will make the settings functions easier to maintain going forwards and simplify additional functionality such as shortcut keys.

See iwbnwif/qucs_s:static_settings_object for the new classes and an example of usage.

Please note: This is 100% compatible with all existing settings and can run in parallel with QucsSettings if wanted.