Better IB support for BTRControls

[indragiek]

Not sure if this is even possible, but it's currently clunky to use BTRControl's from Interface Builder because you can't set a target/action without doing it programatically. I think doing target/action connections might be limited to NSControl subclasses in IB, but maybe we can figure out a more creative solution?

[avaidyam]

It's impossible because Interface Builder only gives the selector outlet to NSCell and NSControl subclasses. I'm looking for a way around this with Mocha, something like IBOutletCollection might help, but that too is iOS only.