Use sqlite3.Row factory in Flaskr (#588)

As pointed out in issue #588 sqlite3.Row should be used instead of using casting to dict(). Also altered the "Easy Querying" Patterns example to include the more correct way to return rows as dicts. Did not touch Tutorial examples ("Views"), as these are not up to date with the current Flaskr code, and the "Show Entries" section points out the "Easy Querying" section on how to convert to a dict().