Test: Backlog: Hack for creating stories

This is for rudimentary end-to-end testing
of creating stories asynchronously, which
is something we want to nail down soon.
Refactor: Move findStoriesById to dataAccess layer

Build the story list in the data access layer instead
of Express. Also return the 'new' story when it is
added to the database.
Have server create ids when adding stories

When adding a new story into the backlog,
make the server be the only one who cares
about what the next story's id will be.

Also use CouchDB uuids for our ids instead
of ints. This is probably how we want our
data to be in the longer term, though we
might add a person-friendly id in the
future.
Fix: Backlog: Update model when moving stories

When we were moving stories, the array that the
backlog is bound to was not being updated. Now
we update the array every time stories are moved.

Not the most elegant solution, but a solution
for the time being.