Use smart quotes in document filter page titles

* http://smartquotesforsmartpeople.com/
Give featured list filters more room

* Match document list filters by using the same sized grid elements
* Remove custom span2 styling
Emphasise filtered table header

* Use table-header styles brought across from govuk_admin_template
* Make feature filter and document filter table styles match
Add heading to feature filter search results
Add clearer 'no documents found' messaging

* Use the no content styles brought across from govuk_admin_template