New variant functions instead of pseudo class methods for init methods

[progrium]

This is a significant change that impacts commonly used convenience constructor methods. These new ones are more Go idiomatic, don't get in the way of actual class methods with the same name, and actually call Autorelease to honor the memory management policy. You now need to use objc.Retain in some cases where you might have gotten away with not.

[tmc]

Some treatment of Retain() in docs will make sense but this looks like a move in the right direction. LGTM.