Add guidelines for view method names

[marijnschilling]

When we start using xibs we will have to name the IBAction methods and the corresponding delegate methods to the ViewController

@IBAction func didPressLogin(_ sender: Any)

In the spirit of this article: http://khanlou.com/2016/09/swifty-delegates/ we agreed on naming the delegates like this:

func didPressLogin(on authView: UIView)

[designatednerd]

@marijnschilling With the pending revisions to the code standards we're moving away from prescriptive naming. Would you mind if I closed this out?