Implement new styles for document filter summary

 - Large number prefixing summary
 - Remove grey boxes surrounding chosen options
Remove unused chosen class
Redesign feed and email buttons

 - Rename buttons and add text explaining them
 - Show panel with copy/pasteable link when clicking on "feed".
   This fixes the problem of people clicking on "feed" without
   knowing what it means, then getting a page full of scary XML.
Remove "all topics" and "all orgs" from filter
Display document type in document filter