Make it safe to run Flash in TBB

Here's what we wrote: "The Tor Project will design a sandbox to allow Tor Browser Bundle users to safely use Adobe Flash plugins, or compatible technology, with a majority of web sites on the Internet. We will work with experts in the field of sandbox technology to develop a solution for Microsoft Windows, Apple OS X, and Linux operating systems. This implementation will be integrated into the alpha-release branch of the Tor Browser Bundle packages."

Originally we'd been planning to have trams lead this project, but it's been a year or more since we originally proposed it so we should try to rope him back in. I'm assigning to Mike to start with, since we need his help deciding what direction to take. We have basically a full-time person of funding to devote here, so let's do it right.