Add convenience factory methods to create NSDictionary, NSArray, and NSSet

[hprange]

As per JEP 269, Java 9 defined library APIs to make it convenient to create instances of collections and maps with small numbers of elements. This pull request introduces a similar concept for NSDictionary, NSArray, and NSSet. It provides convenience factory methods to create NSCollections in a less verbose, concise, and uniform way.

Usage:

NSDictionary<String, String> dict = NSDictionary.of("k1", "v1",
                                                    "k2", "v2");

NSArray<String> array = NSArray.of("e1", "e2", "e3");

NSSet<String> set = NSSet.of("e1", "e2");

[luizalfredo23]

I can't wait to save some lines of code by creating an NSArray with some items in just one line, countless times when I could have used it.

And of course, creating NSDictionary would be a lot easier.

[darkv]

@luizalfredo23 with the Wonder versions of those classes this was already possible since long ago like
NSArray<String> array = new NSArray("e1", "e2", "e3");

[luizalfredo23]

@darkv

@luizalfredo23 with the Wonder versions of those classes this was already possible since long ago like
NSArray<String> array = new NSArray("e1", "e2", "e3");

With Java 11 I've been using List.of so I think it would be nice using NSArray.of, but I did not know about the constructor, I'm using it right now. Thanks.