Feature/gs evk uart example

[gssammy]

Description

Using AP's example framework to add a basic driver for testing ASCII phrasing when connected to the EVK on telem 2.

General Implementation Details:

• Starts UART ports on Telem 2 (connection to EVK) and Serial0 (for debugging)
• Simple parsing state machine
• Checks logic for detecting the start of packet, type of packet, and checksum

Next steps

• Implement handle_packet to decode message payload from ascii encoding into appropriate int fields
• Copy implementations here to Add Support for AnelloEVK as an External AHRS system #2