Consider simplifying ExternalApp structure

[Mazyod]

Having added applications inherit ExternalApplication gives us a lot of flexibility, but I am starting to question the need for such a flexible design. Perhaps making it a simple struct instance would reduce all the boilerplate code written for the added apps... Need to investigate.

[Maryom]

This looks great, I have a question we used ExternalApplication instead of calling openURL because of this 👇🏼
https://twitter.com/nicklockwood/status/595347585747001344

[Mazyod]

nah, this is just a refactor to organize the library API

[Maryom]

Salam,

I think this will help, do you agree?

[Mazyod]

This is real nice, we'll need to support this when it comes out, yes.

[Maryom]

Salaam,

I need to know still we need to support iOS 9 ? because I think it's better to use iOS 10 new method:
open func open(_ url: URL, options: [String : Any] = [:], completionHandler completion: (@escaping (Bool) -> Swift.Void)? = nil)

There is a solution if we need to support iOS 9 but I just need to know to save some lines of code.

[Mazyod]

This is a different feature, so I created a new issue for that here: #82