Iglistkit: Refactor macOS example to use NSCollectionView

[rnystrom]

As evidenced in #342 and #337, the changeset produced by the diffing algorithm is not compatible with NSTableView since it expects its batch updates to be made incrementally (even when using batch updates).

So that we don't lead anyone astray, we should refactor the example to use an NSCollectionView that should work the same as UICollectionView when batch updating.

[Iron-Ham]

I'm down to jump in on this one when i get back from traveling.

[rnystrom]

@heshamsalman all you!

[Sherlouk]

@heshamsalman Quick ping! -- when are you back from travelling?

[Iron-Ham]

@Sherlouk just made it back last night!

[MoralAlberto]

Hi @heshamsalman, any news about the example with NSCollectionView? thanks!

[Sherlouk]

@heshamsalman Still intending on doing this one or would you like someone else to pick it up?

Don't mind having a look!

[Iron-Ham]

@sherlouk ah, this totally slipped through the cracks 😔

The night owl in me says to do it, but the realist in me is looking at the sprint I have ahead of me. If you wanna pick it up, go for it.

[weyert]

I am working on this now. I just wished Xcode wouldn't crash each time I drag in a Collection View 😅

[weyert]

Phew, quite a pain to get the NSCollectionView in the storyboard so I ended up copy-pasting it from Ray Wenderlich tutorial. For some reason when you drag a NSCollectionView into the view controller (after removing the table view bits) it crashes Xcode 8 and 9.

I have made the necessary changes to make it work with the NSCollectionView as this class doesn't support row actions I have added a button instead.

@rnystrom @jessesquires

[weyert]

I have also fixed the issue that you couldn't see the collection view animations. The backing view had to have Core Animation enabled so I did this in IB and made a comment in the code. Guess this is 'by default' in UIKit/iOS?

Looking forward to hear from you, what you think of this PR. Thanks!