Small fixes to do with speech "bubbles"

Fixes https://github.com/mysociety/sayit/issues/232 by only showing the "Unattached speeches" (now "Speeches without a section") title when there are actually sections the speeches could alternatively be put into. This way, people who don't use sections will never see the heading, and people who do will be able to understand what the extra speeches at the bottom of the page are for.

Also, styles the speech "bubbles" under that heading to match the ones on a speaker detail page. And fixes a small bug with breadcrumb doubling in those bubbles.