Geist Watchdog does not discover airflow or THD sensor

Patch file attached to add support for the airflow and THD external sensors on Geist (now Vertiv) Watchdog 15 and 100.  

I have Watchdog device with these external sensors and have tested and confirmed that the changes do work correctly.   I only have a single instance of each sensor, so have not tested in the case of multiple.   I do have multiple temp sensors connected and those work fine and the new ones are defined the same way, so I expect they should work.