Rip out or redesign the topic system

Original LP Author: Barry Warsaw , LP Link: https://bugs.launchpad.net/bugs/975705

At Pycon, it was observed that the topic system as it exists in mm2.1 isn't really all that useful. Terri had some thoughts about that in regards to work that Systers did. This is mostly a placeholder for future ideas and to get it out of my TODO list. :)