Document the (likely) on-disk location of settings clearly

[chris-hatton]

I'm using the JVM target on macOS, with no-arg Settings() API and despite following up the documentation for Preferences.userRoot() I am unable to find where the settings are stored on disk. This is really important for development, to be able to inspect/backup/clear them etc. Suggest this would make a valuable improvement to the docs.

Edit: This is actually driving me nuts(!) The settings are persisting between runs alright, I just can't find where they are! Inspecting the Preferences object in debugger doesn't enlighten much either, giving an absolutePath of /, but I wouldn't expect that App to be successfully writing to the root of my drive, and sure enough it isn't. Tried lsof but can't catch the App in the act of accessing the plist. I'm going to have to switch to using the arg-ful constructor for Settings just to be able to specify the file location.

[russhwolf]

I'd rather defer to the backing API documentation than redocument it and risk introducing errors or confusion.

You're almost certainly better off not using no-arg if you care about these details. But it is (apparently) possible to supply a custom PreferencesFactory which might allow you to pass whatever customization you need. See notes at the end of the Preferences javadoc.