[Unison-hackers] Update and cleanup plan for the macOS UI

[Michael Roitzsch]

Hi Benjamin,

> All these changes should be very welcome.

Good, I’ll get to it then.

>> * What do think about localization? Is it too much effort to maintain in the future? Otherwise, I might also consider a German localization.
> 
> We’ve considered localization in the past, but the hesitation has indeed been that it might be hard to maintain (and, relatedly, might make a lot of the code quite a bit uglier).

Got it. I’ll not go there.

Thanks also for the advice of packaging as multiple PRs.

Michael