Activities/Toaster/USB

Quite a bit of work has been done to make creating USB sticks easy with various tools. We don't want to recreate the wheel. We do want to know how to:


 * After the Toaster Activity has been started, detect if new USB sticks have been inserted
 * Provide a "simple" UI for providing Sugar on a Stick and/or writing .iso files to sticks so they are bootable
 * act as a front end to whatever tools and code we package in the Toaster activity to get the work done