discuss config file location improvements

[rkitover]

@lhmouse @akuropka

Following up on #42, Here are my suggestions for locations to search for the config file, we can discuss and I'll open a PR etc..

User Mode

Order	Location
Primary	%APPDATA%\nano\nanorc
Secondary	%USERPROFILE%\.nanorc
Global	%ALLUSERSPROFILE%\nano\nanorc

Admin/Elevated mode

Order	Location
Primary	%ALLUSERSPROFILE%\nano\elevated_nanorc
Secondary (for backcompat)	%ALLUSERSPROFILE%\nanorc

%ALLUSERSPROFILE% maps to C:\ProgramData on recent versions of Windows.

[lhmouse]

Thanks for the suggestion; looks reasonable to me.