#19308 - Store menu settings in the avatar data file

I ended up going a bit further (and got off to a later start) than initially intended on this to allow for runtime getting and setting of settings as needed.  Currently, setting and getting of parameters are consolidated in the read and saveSettings functions in Application.

Though really, this is just for convenience; getSetting* and setSetting* functions can be called anywhere in Interface, and any new settings will automatically be added to the settings map upon first attempting to set them through setSetting*.

All settings in the map will be serialized upon calling Application::saveSettingsFile, and likewise are all read and inserted into the settings map within Application::readSettingsFile.

For generic data storage, both keys and values are stored as strings, interpreted on demand as necessary.