Implementation of the sensor VEML7700

[Dr-Gandalf]

This code, implements the measurement of light (lux and irradiance), using the veml7700 light sensor. This pr is related to the pr #498 on the protobufs repo

It also modifies the MQTT client to publish the new signals to the mqtt server.

[thebentern]

Looks good to me. Upstream protobufs have conflicts now though

[caveman99]

@thebentern now you know why i tell people every time not to push the protobuf subdir or generated files. That always explodes

[thebentern]

@thebentern now you know why i tell people every time not to push the protobuf subdir or generated files. That always explodes