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.
Ah, okay.  So to be clear, the expectation is that the Api method which tries to get the data will definitely set Env.message if there's an error --- you're just doing this to be paranoid in case due to a code bug, we don't import the error from the server?  If so, okay, that's fine.