Data: Add story update function to APIs
Backlog: Add serverStories wrapper

... so we can notify the server when we make
a change to stories.
Backlog: Persist story order

Save the stories to the server when they
are moved.
Backlog: Keep isFirstStory up to date

Now the system always knows what the first
story is, as the data is updated.
Fix: Backlog: Make isFirstStory correct on client

isFirstStory is now accurate on the client side of
things at all times.
Fix: Backlog: Persist when appropriate

Clean up the persistance code as well as
the setFirstStory stuff, so that it works.