sugar-rpi-os v1

- Generate an RPi OS with sugar shell insatlled
- Add some activities (default ones + tower-of-hanoi, number-guessing, flappy (by Vaibhav), turtleart-activity, and rpi_control_center)
- Temporary fix the browse-activity issue (remove v207 that comes from apt, install v208, install dependencies)
- Lacks the RPi sensor libraries for now. TODO: clone rpi-lib from my repo and paste it in python3.xx/site-packages (or as the readme directs).