Correct path to preferences file for Windows

[terrillmoore]

The path to preferences.txt was incorrect for Windows. I did not update the HISTORY for this change, as this is just correcting a typo.

The path as given is right for Windows 7 and later; I think it is right for Vista, wrong for XP, but do not have systems for testing.

[per1234]

The macOS/Mac OS X path should also be documented. I believe it's /Users/{username}/Library/Arduino15/preferences.txt

[terrillmoore]

I don't have a Mac for testing. Perhaps issues should be filed for:

1. Changing / to \\ for Windows systems, where appropriate,
2. Fix the Windows path for the sketchbook: My Documents/Arduino doesn't exist as such on Windows 10, and (as @PaulStoffregen pointed out on Fix path to preferences.txt on Windows #6060) the right syntax on Win10 would be something like %USERPROFILE%\Documents\Arduino. I'm not sure what it would be on XP (where My Documents still exists).
3. Also as @PaulStoffregen pointed out, consider using %LocalAppData%\Arduino15\preferences.txt
4. Changing Mac OS X to macOS (for consistency)
5. Fixing the macOS path description(s).

For 1 & 2, My feeling is that anyone using Arduino from the command line on Windows is very likely to be using git bash, or the like, not cmd.exe; so they're going to be more interested in a ~-based specification. But perhaps we need to document cmd.exe and assume that people doing advanced things can figure it out. (Now that there's Ubuntu-on-Windows, bash could be git bash, could be Ubuntu bash, or could be cygwin bash.)

[per1234]

I don't have a Mac for testing

I don't have a Mac either, I found that information on the forum so I wouldn't feel comfortable submitting a PR for the change without verification.

2. Fix the Windows path for the sketchbook

It seems most simple to just remove any specific sketchbook path descriptions for all OSs from the documentation and instead refer people to sketchbook.path in preferences.txt (which is already documented) or File > Preferences > Sketchbook location (which is not currently in the documentation).

My feeling is that anyone using Arduino from the command line on Windows is very likely to be using git bash

I don't think that's a safe assumption. CLI will frequently not actually be used directly from the command line but instead from batch files, shortcuts, or other applications.

[facchinm]

the correct path in windows is %APPDATA%/Local/Arduino15/preferences.txt, any other way to express it is not compliant (although it's used by git shell or cygwin or similar)

[cmaglie]

There is also %LOCALAPPDATA%/Arduino15/preferences.txt

[facchinm]

On osx the path is $HOME/Library/Arduino15/preferences.txt, just checked. The Linux one is ok but I'd replace ~ with $HOME