Sensor integration checks

[oscgonfer]

Given the "larger" amount of sensors we are integrating lately, we would like to have documentation of:

• How to integrate a sensor
• What to check when doing it
• How to test it (both quick and long term)

We can discuss this here and further down the line document it in the docs so that other people can also do it.
Finally, given the big effort of the mux branch, we would like to document that so that the integration is a bit easier for other people to integrate sensors in the SC firmware.

This is also linked to the fact that we might have a longer supported sensors list and we should somewhat automatize these tests to avoid wasting time during the tests.

[pral2a]

Strategies on Production Testing

1. Each sensor (and potentially components) to inherit a test class where particular validation functions are written directly in the main firmware. That way the hardware can perform a self validation, even while in normal operation mode.
2. Use existing commands available on the shell (and potentially add new ones) and implement the test procedure on a python script that executes and validates the hardware remotely over serial. That will be part of smartcitizen-tools