Added a page to display buttons and sets

Resolves #912

http://jenkins.buttonweavers.com:8080/job/buttonmen-AdmiralJota/342/

This also involved tweaking the python client a bit, so that should be tested too.
Right, exactly. I think this happened to me once on some other page (although I don't remember the details now), so I've started doing it out of habit, so we don't get a mysterious blank page in those cases.