Database: Use generated id instead of patron email

Using the patron's email address as the primary key
for each document record just felt like a really
bad idea.

Now we use a 'byEmail' view to retrieve the patron's
record, which is pretty rad.
Database: Add 'things' view; integrate with server

Add a view to get a patron's list of things, given
a username.

Take advantage of this view within our data API,
adding a GET /things/:username handler.