Current usage of `settings.add_on_change` is errorneous

[benweier]

Current usage of `settings.add_on_change` is errorneous

[benweier]

Thanks @FichteFoll

I finally got around to addressing the issue. I hope you don't mind I was inspired by the way you initialise FileHistory and I modelled Themr off that. On closer inspection of other areas of Themr I found that it was loading multiple preference objects when it didn't need to be, so I refactored a bit to reduce them down to a single preference object per settings file. I also took the opportunity to clean up a few functions to improve their separation of concerns.

[FichteFoll]

Sure thing. Instance handling has actually changed already as I'm now using a metaclass instead of the instance classmethod.

I also use many different approaches for state sharing in my plugins, but I still haven't really decided which way is the best and pretty much decide what I'm going to use on a case by case basis (another example is InactivePanes). FileHistory was written by @jbjornson btw and I just help maintaining it.

[benweier]

Big thanks to you both then :)