Set up configuration settings for PPP-RTK receiver and sets up json output from send data to sfy

[edwinrainville]

Overview: This update adds all configuration settings to the PPP-RTK receiver and also sets up the json document that will send data to the sfy from the receiver. The data sent to the SFY includes: Time (UTC), time accuracy (ns), lat, lon, height above mean sea level (geoid, WGS84 in mm), horizontal accuracy (mm), vertical accuracy (mm), carrier solution, and gps fix type.

Next Steps:

• adjust the navigation solution frequency to 20 Hz, it is currently set to 1 Hz for easy testing
• need to set up another json document to output the correction data, it might be useful to have later on as well in case there is an issue with integrating it realtime

Other Notes:

• the SPARTN keys file is ignored in the repository, so the decryption keys are not available to the public

[gauteh]

Great!

If we should send both types of messages we should:

• tag the message with a JSON field e.g. 'type': 'pos'.
• always send a pos paired with correction message to keep things predictable and easy (or handle sporadic correction messages on the sfy side)

Also unsure what we have bandwidth for, but I think we should have plenty still.

Merging!