Neo2 keyboard layout file for macOS.

This is based on the file provided by neo-layout.org, but has a number of improvements:

• Improved caps lock layout: Top row still provides the numbers (special symbols require shift in addition to caps lock), letters are switched to lowercase when shift is pressed, allow to type layer 3 symbols with mod 3 when caps lock is active.
• Fixes to the handling of M3+Cmd to increase compatibility with shortcuts (though, shortcuts involving M3 can still be problematic and will remain so for the foreseeable future).
• A few unassigned keys in the layout have been fixed.
• Fixed layer 4 minus.
• Fixed the layout of the Ctrl modifier to work in MacVim.
• Fixed compose function for ñ.
• Fixed Ctrl+J.