0.8dev: Fixed regression in r1570616: the product at scope is no longer the default selection. Refs #727.

The code in `theme.py` was also refactored to simplify preparation of the `options` dictionary.


git-svn-id: https://svn.apache.org/repos/asf/bloodhound/trunk@1573459 13f79535-47bb-0310-9956-ffa450edef68