Add Non-Volatile Revision To Firmware Builds

[kb1lqd]

For better release tracking a non-volatile revision number should be saved into firmware memory to ensure debugging can adequately track revisions being used. This variable should not be able to update other than by reprogramming the device firmware. Automated updates are preferred but manually updating revision for each release can suffice for short term.

[kb1lqd]

Committed update in ec794c1

I programmed firmware with revision "5" and decoded a proper firmware revision in the updated software as shown below:

Verified in debug mode that firmware revision was correctly being copied into packet:

Verified output of decoded data correct per software Issue FaradayRF/Faraday-Software#65:

[kb1lqd]

Bug patched in #66