[Development] QSettings refactor updates

[Morten Johan Sørvig]

> 
>> Mac people: do we need access to plist files?
> 
> Plist is the format for application and other settings on OS X, and there are native tools for nicely editing these. Ini is highly alien on OS X.
> So, I’d answer yes.

On the other hand, git uses the ini file format for the config files also on OS X.

I see this as two separate use cases: 
1) Cross-platform API for managing application settings.
2) API for reading native settings, following the conventions of the platform

To what degree was QSettings successful in combining these? Focusing on ini+json as supported formats will certainly simplify the implementation work.

Morten