Why NSMatrix has been removed?
The suggestion to use radio-style NSButton is NOT equivalent. With NSMatrix, I could bind `selectedTag` to the corresponding enum property in model with just one binding, mapping radio buttons directly to numerical values of enum options like 2, 3, 5.
There is no way to do that with NSButtons without adding tons of boilerplate to the view controller — a getter method, a setter method and key-value observation for EACH button. It also requires binding each radio button separately, which adds maintenance headache. And it requires silly `doNothing:` action, because without some action assigned, they do not work together as a single radio group.
Why would you complicate developer's life for no reason?
