Updates for final launch

See merge request beagleplay/docs!1

Add accessories section updates

See merge request docs/docs.beagleboard.io!39

Add BeagleBone Accessories section

See merge request docs/docs.beagleboard.io!38

* Add instructions for pre-built binaries

See https://git.beagleboard.org/docs/sphinx-build-env

Newest board family should go first. Microcontroller boards may need separation.

WIP: Add some initial instructions for flashing the board using the production firmware. Taking a pause to save my work. I need to figure out how I can download from the command-line, rather than the web browser so these instructions don't have to change drastically.

Jason's lateast updates

See merge request docs/docs.beagleboard.io!36