README Cleanup

@jimblom - here's my stab at README cleanup for this repo.

Things were already pretty clean. Here's what changed:

* Standardized the image/SKU/name link and consolidated the description text into that top section
* Added contents section and cleaned that up a bit
* Added license sections - license info still needed for hardware
* Removed redundant information from the firmware directory readme

Let me know what you think. Do you know what the hardware license is on this board?