Query config and cursor

I added two features to db/utils.py.

1. Modified how cursors work so get_cursor returns the cursor for the most recently returned row. Previously you could only get the cursor after reading all the results from a query.

2. Added the ability to configure the underlying app engine query, so you can change the read policy, deadline, etc. The available options are here:

https://developers.google.com/appengine/docs/python/datastore/queryclass#Query_run