Add unique id/label in the mqtt log message

Hi,

When i sent a message to the Farmbot i can sent a unique ID/label with the command from an external application. It would be nice to see this ID/Label in the logs again so i can relate the succes messages to command that was send earlier.

For background info, see:

This feature would require FarmBot OS to keep track of which command caused a log message to be created.