Dailybread Changes

1. Modified the dailybread module to not break when there are no Portions in the database.
- Modified the today() method in models.py to return an empty Portion if no approved Portions exist in the database.
- Modified TodaysPortion in views.py to raise a HTTP 404 exception if the supplied pk does not exist in the database.
- Modified the index.html page to display a message when there are no approved Portions in the database, including a link to the submit page.

2. Removed some trailing spaces in the dailybread urls.py file.

3. Added some things to the dailybread Portion admin.
- Rearranged the order of the list display so that title comes first (the first item is clickable for editing, so it's best to have it as some kind of text, not as a boolean).
- Added search fields for title, text, and reference.