Show breadcrumbs to current topic

[littledan]

During a reply, show the description of the parent topic in the UI at the same time. Also, consider allowing returning to the parent topic after a reply is done. This way, speakers won't feel like they are "giving up their slot" by clicking done and working down through the replies.

[bterlson]

Good idea. Related to #5 (adding current agenda item to the UI as well).