Add views for creating a story and managing a story's storylines

This adds views for creating a story and managing a Tale's storylines.

To know when a user creates a story, assign a `CreateStoryViewControllerDelegate` to `CreateStoryViewController.delegate` and implement the `createStoryViewController:createStoryViewController:didCreateStory` method. The view controller will call the delegate method with a new `Story` object.

The StorylinesViewController is used to manage a story's storyline. Users can create a new storyline, delete storylines and rearrange storylines. The view isn't yet wired up to models and needs to implement a form of ACL to limit the storyline deletion and reordering if the signed in user isn't the owner of the story.

/cc @snekkalapudi, @rvharsha